Heat the oven to 180C/160C Fan and line three 20cm/8inch sandwich cake tins with baking parchment – leave to the side.
In a stand mixer, beat together the butter and caster sugar for a few minutes until light and fluffy. Add in the flour, eggs, and lemon zest and beat again briefly till combined – try not to overbeat!
Carefully fold through the 300g of fresh blueberries into the mixture.
Divide the mixture between the three tins and smooth it over – bake for 25-30minutes until the cakes are golden and when the cake springs back (skewer should also come out clean)!
Once baked, leave the cakes to cool in their tins for 10 minutes or so, and then remove and leave to cool fully on a wire rack. If the cake has domed slightly, leave the cake to cool upside down to flatten it slightly so its easier to decorate later!
For the Decoration
Beat the butter with an electric mixer for a couple of minutes to loosen it – Gradually add the icing sugar on a slow speed until it is combined, add the lemon juice, then speed the mixer up and mix for 3-4 minutes until thoroughly combined and smooth.
If its too thick, gradually add the boiling water until you reach the desired texture – I usually add 2 tablespoons! Keep on beating for 2-3 minutes until whipped and silky smooth!
Using your favourite piping tip, I used a large round tip, pipe the buttercream onto the bottom layer of the cake. Add some jam, I drizzle it slightly to make it look pretty, and add the second layer, and pipe buttercream on again, and then the jam again, and add the final cake layer.
I then pipe the rest of my buttercream on top, and add on some extra fresh blueberries!
This cake will last at room temperature for 3 days. I used a a large round tip to decorate my cake, but you can use any really!I used Blueberry Jam because I wanted an extra Blueberry hint, but this is optional. Also, you can use lemon extract in the sponge and buttercream if you wanted instead of the fresh lemon zest and juice. The cake may take a little longer to bake due to the moisture coming from the blueberries, but don't worry, just wait till a skewer is clean and it's not making a bubbling sound anymore. You can try frozen blueberries, but be warned they may create even more extra moisture.I love this style of cake as you can tell from the few I have made, and I happen to have 3 8″ tins, if you don’t have 3 tins you can make a smaller version of the cake, use 300g of everything in the cake mixture rather than 400g, 6 medium eggs (and it might take an extra 5-10 minutes to bake) and use 2/3 of the decoration recipes!