Rainbow Cake!
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A delicious and bright rainbow cake with vanilla buttercream frosting, a pink drip and sprinkles!
Rainbow cake
Oh hellooo most requested recipe OF ALL TIME. I am not even joking, this recipe has been requested over and over again and I am ~finally~ posting it on to my blog! It’s taken a fair old time as I wanted to get it right!
I love all things cake, we all know this, but a rainbow cake is something else. The absolutely insanely bright colours, the sweet taste, and all things cute take it to a different level entirely! It is just glorious.
Disclaimer
So… I will say from the beginning that this recipe uses lots and lots of ingredients, and it is a humongous cake! Like, its 6 layers of cake, and all the buttercream in-between the layers, and all the decor on top!
And I will also say from the beginning… YES I KNOW THE RAINBOW HAS SEVEN COLOURS. This cake, is only six. When baking this cake, I just find making 6 colours so much easier, and you can see the obvious differences. I am not bothered about the seventh!
Red, orange, yellow, green, blue and purple… the main colours you need in your life. I did slightly compensate for the lack of seven colours by adding in a pink drip on the outside but we will get to that later.
Sponge
For this cake, I did make probably the biggest one tier cake ever. It’s about 8-9” in height, and uses so many ingredients. Because it is a six layer cake I decided to make it in two batches. So three layers at a time, so therefore you still only need three tins!
I made the cake a 600g mix, so that it’s super easy to split into two batches. The best way is to weigh 5-6 medium eggs, and get as close to 300g as you can, for example 312g, and then match the butter, sugar and flour to that weight.
Colour
Then, you mix it all together like normal, and then split into three bowls. It doesn’t matter which colours you do first, but I did red, orange, and yellow together, and then green, blue and purple.
The oven temperature is a bit lower than normal, as I don’t want the sponges to brown too much. This also comes somewhat from the brands of colours that you use! Red food colouring, orange food colouring, yellow food colouring, green food colouring, blue food colouring and purple food colouring. for the sponge mixtures!
Buttercream
Once my sponges are baked, I leave them to cool completely and freeze them wrapped in clingfilm over night so that they are easier to decorate the next day – but this bit is completely optional of course!!
For the buttercream, you do use 750g unsalted butter and 1500g icing sugar, which technically is a little obscene but the amount of servings from this cake is huge so please don’t be a negative Nelly about the sugar content!
I make my buttercream like normal by beating room temperature unsalted butter on its own for several minutes to make it really loose and supple, and then I gradually add in the icing sugar! I make sure to beat this for quite a long time.
White food colouring
You can do several methods to get whiter buttercream, by beating the butter on its own for a lot longer, or using a smidge of purple buttercream to counter act the yellow, but I love using this white food colouring! It looks amazing on my white chocolate drip cake and I haven’t looked back since.
I add a little at a time and keep beating it very well to make sure its really white and bright to contrast against the colours of the sponge! Making the buttercream whiter is completely optional of course though.
Decoration
When I am starting to decorate the cake, I dollop a few tablespoons of buttercream onto each sponge and smooth over, making sure to get the order of the colours in the sponges correct of course…!
Once you have layered each sponge you need to do a crumb coat by using as little buttercream as possible around the edges to seal in the spare crumbs from the sponges! I then chill the cake for a while to firm it up before adding another layer of buttercream on top.
I use a large metal scraper to decorate the sides of the cake, and a small angled spatula to also help cover the sponges – and its much easier and you are going to get a smoother finish using these as well!
Sprinkles and drip
Just as I have finished the buttercream I carefully press in some rainbow sprinkles to the bottom of the cake for a bit of colour and I just love the design – be warned, sprinkles will fall off at this point so beware! After this, I chill the cake again!
For the pink drip, I use white chocolate ganache with this pink food colouring added in. Its a super bright colour so you don’t need add too much and it means you get the best coloured drip ever!
Finishing touches and tips
I then pipe on the leftover buttercream and add on some more rainbow sprinkles and the best cake ever is finished! I am in love with the sponges and how bright and pretty it is – but the key point to make, YOU NEED TO USE GOOD QUALITY COLOURS.
Using supermarket colourings, will NOT work as well, or maybe at all… so please don’t waste ingredients by doing this! The colourings are 100% worth the investment as they last for so long! Any questions, leave them below in the comments and happy baking! x
Rainbow Cake!
Ingredients
Cake
- 600 g eggs (weigh eggs in shell) (about 10-12 medium eggs)
- 600* g unsalted butter
- 600* g caster sugar
- 600* g self raising flour
- 1/2 tsp red, orange, yellow, green, blue, purple food cololuring
Buttercream
- 750 g unsalted butter (room temp, not stork)
- 1500 g icing sugar
- 1 tsp vanilla extract
- 1-2 tsp white food colouring
Decoration
- 180 g white chocolate
- 75 ml double cream
- 1/2 tsp pink food colouring
- Rainbow sprinkles
Instructions
For the Cake
- Preheat your oven to 160ºC/140ºC fan and line three 8"/20cm springform tins with parchment paper and leave to the side for now.
- Weigh 5-6 medium eggs in their shells and get as close to 300g as possible (e.g. 312g)
- Then add 312g of butter and caster sugar to a bowl and beat until light and fluffy.
- Add in the eggs, and 312g of self raising flour and beat again until smooth.
- Bake the cakes in the oven for 30 minutes (or until baked - test with a skewer).
- Once baked, leave the cakes to cool in the tin for 10 minutes before removing to a wire rack to cool fully.
- (You can wrap the sponges in clingfilm once they have cooled and freeze over night to make decoratin easier but this is optional!)
Buttercream
- Once all of your cakes are cooled, you can make the buttercream.
- Beat the room temperature unsalted butter on its own for a few minutes to soften it and make it supple.
- Gradually add the icing sugar beating very well each time until its all mixed in.
- Keep beating and add the white food colouring and vanilla extract and beat for a few minutes.
Buttercream Decoration
- Using a 10" cake board, add your first sponge. I start with purple as its the bottom colour.
- Add a couple tablespoons of the buttercream on to the sponge and smooth over. Repeat this with blue sponge, then green, yellow, orange and finally red at the top.
- Using a small amount of buttercream, smooth over the sides of the cakes and fill in any gaps and create a crumb coat.
- Refrigerate or freeze the cake on the board for an hour or so to chill and firm to make the next stage of decorating easier.
- Once chilled, add on lots more buttercream around the sides of the cake with a small angled spatula, and smooth over using a large metal scraper until the sides of the cake are smooth like in the photos!
- Carefully press some of the sprinkles into the bottom of the cake using the palm of your hand to create the sprinkle effect!
- Once this has been done, refrigerate again whilst you make the drip!
Decoration
- Add the white chocolate and double cream to a bowl and heat in a microwave in short 10 second bursts stiring well each time.
- Once melted and combined, add the pink food colouring and mix until smooth!
- Add the pink ganache to a piping bag and carefully cut off the end and drip down the sides of the cake. The more you push over the side of the cake with the piping bag, the further it will drip!
- Add the leftover buttercream to a piping bag with your favourite piping tip and pipe swirls of buttercream onto the top of the cake (like I have done in the photos)
- Finally sprinkle on some etra sprinkles and leave the cake to set in the fridge fully.
- In the hot weather I store the cake in the fridge until it has been portioned.
Notes
- This cake lasts 4-5+ days once made!
- The colours that you use and what order are up to you, this recipe is just how I did it! You can swap up the order or whatever you prefer!
- You should avoid supermarket colours as they are not strong enough.
- In this recipe use:
ENJOY!
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J x
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I’m going to try making this cake for my goddaughters birthday. She’s allergic to dairy so I was going to switch out the butter for dairy free butter but I’ve noticed some of your vegan cake recipes use vegetable oil instead of butter. Is that something you would recommend for this one too?
Hiya! If you are after just a dairy free version, I would just use dairy free butter! Hope this helps! x
Hi Jane! I’ve been asked to make a gender reveal cake for my cousin and this would be perfect in shades of pink or blue so could I do just 3 layers if I half the recipe as 6 might be too many? I also have Wilton gel colours, would they suffice? Thanks in advance 🙂
Hiya! Yes that sounds great, wilton gel should be fine! Hope this helps! x
Hi Jane! I’ve been asked to do a gender reveal cake for my cousin, so wanted to do this but on a smaller scale! Could I just half the amount to do three layers and then colour appropriately? I also use Wilton gel colours, will they work as well? Thanks in advance 🙂
Yes absolutely, this should be fine! Hope they love it! x
Hello Jane, was wondering how I could make this but with only 4 layers? Nor sure om ingredients!
Hello,
Could you roughly tell me how tall this cake is? I need to store/transport it in a car for a few hours and wondering if it’ll fit in my cool box! I’m worried it won’t fit!
Hiya! At a guess – id say around 7-8″. Hope this helps! x
Hi Jane! This rainbow cake looks amazing! I’m planning on making this for my friend’s daughter’s Christening for next sunday, but she’s asked for a salted caramel frosting/buttercream instead of vanilla. What would be the amounts/ingredients for salted caramel frosting/buttercream? Also, is there any way of making the frosting white or is that impossible if it’s a caramel one? Thanks! 🙂
Hiya! Take a look at my salted caramel cake recipe! Sadly you probably will not be able to achieve white. Hope this helps! x
Hi Jane
I love your recipes so much but need help. I want to make white chocolate coating but in a colour. Is this possible and what chocolate and dye would go together that I can do this.
I tried melted white chocolate and adding a gel food dye in but it didn’t work and gone horribly wrong
I’ve heard candy melts are good please help
Hiya! Take a look at my White chocolate drip cake for the chocolate buttercream, and my ‘my favourite food colourings’ post where I link which colour works best with chocolates! Hope this helps! x
Omg omg!! Let me just say this was my first time trying to bake a cake and oh my gosh it’s literally turned out stunning!! I wish I could upload a picture because WOW
Would it be the same amounts for a 10”cake with 4 layers? What about baking time? Thank you!
Hi Jane
Would you recommend putting cake dowels in to make the cake more sturdy and less prone to falling over?
Hiya! You can do – but this cake should be fine without also! Hope this helps! x
Hi, to remake one sponge layer? Would it be 100g of each ingredient?
Hi Jane. I love doing your recipes! Going to make this for my 5year old’s birthday, but want to use a 9 inch square tin (as just find them easier to slice up for a crowd) Would you use the same quantity and have thinner layers, and decrease the cooking time, or increase the ingredients, if so by how much?
Thanks Vicky
Might be a silly question but when you freeze the sponges do you need to defrost them before assemble or can you decorate them straight from the freezer
Hello,
I have made this recipe a few times and love it!
How do I convert it for a smaller 6inch cake instead of 8inch please
Hi Becky, did you find this out as I wanted to do this cake but in a 6inch time? Xx
Hi Jane
I’ve made these sponges today ready for my daughters birthday cake at the weekend, but the sponges are only an inch deep and seem sticky on the top. Does this sound right? Or do you know where I might have gone wrong? I weighed all ingredients to match the weight of the eggs. Batch was 306g and batch 2 was 302g.
Thanks
Emma
Mine have done the same! Did you find out why?
Hi Jane, I’d like to make this cake but on a small scale. Can you tell me the weights for a 6” and 7” tin? Also what would you reduce the food colouring quantities too. Thank you.