Refreshing Lemon Blueberry Cake for the 8th Blog Anniversary

You will get a lot of tips for preparing sponge batter in this blog post. For the sponge zest and juice the lemon. Melt the butter in a small saucepan and let cool. Meanwhile divide egg yolks and egg whites into two clean and large bowls, add about 100 grams of sugar to the yolks and about 60 grams to the egg whites. Measure flour and cornstarch into a small bowl. Line the bottom of two 18cm/6inch cake pans with parchment paper and heat oven to 180 degrees.

Using a mixer, first beat the egg whites until soft peaks form, this does not need to become meringue. Without cleaning the mixer, mix the egg yolks until lighter in color and thicker in consistency. Usually this takes a few minutes. Now sieve the flour mixture on top of the egg yolks, add zest and juice of the lemon and one third of the beaten egg whites. Carefully fold and combine, add one more third of egg whites, once combined, add the last third of egg whites and the melted and cooled-off butter. Try not to deflate the batter and carefully fold instead of stirring. Pour immediately into prepared cake pans and bake on medium rack for about half an hour, do not open the oven door meanwhile. Let cool and release from form. You may prepare one to two days in advance if kept in the fridge airtight.

For the filling wash the blueberries and bring to a boil with the sugar and lemon juice, then reduce heat and simmer for about 5 minutes or until the berries release their juice. Meanwhile stir cornstarch in a bit of cold water in a mug until you see no lumps. Add to the berries and cook for at least a minute while stirring. Let cool. I add to add more stablizer to the berries, you should get the consistency of jam. The filling can also be made 1-2 days in advance if kept airtight in the fridge.

For the buttercream heat egg whites and sugar in a waterbath, stir. If you rub a bit of this mixture between your fingers and you cannot feel the sugar anymore, it is ready. Transfer to a mixer and beat until you have stiff and glossy meringue that is room temperature. This may take 10 minutes. Then slowly add chunks of butter. Usually mine looks curdled, which is fine and normal. Reason for this is that butter and meringue have different room temperatures and need to become one. Just continue beating until you have a nice silky and soft buttercream. If it looks soupy, chill before beating again. Add zest and lemon juice last and just briefly beat until incorporated.

In order to assemble the cake first cut each cake in half so that you have four cake layers. Brush the first one with lemon juice, then create a dam with the buttercream by piping a ring all around the edges. Fill one third of the center with blueberry filling. Place the second cake on top, repeat procedure and also do the same with the third. Place the last cake layer upside down so that you have an even cake. Crumb coat the cake and let chill for 30min. Then use more buttercream to frost the cake. You still should have enough left if you wish to "paint" the cake with lemons as I did. I left the frosted but undecorated cake in the fridge overnight.

You are of course free to decorate your cake with lemon slices, blueberries or whatever you see fit. If you want to paint the lemons, try to see your cake as a canvass. I used palette knives and first painted part of the cream yellow, some green, and some I left white. For some more detailed instructions, check this blog post. In order for the lemons to get more dimensions, I also tried to use shades of color, some parts with a tint of red, some with a bit more white, etc. The best thing is, if you are not happy, you can scrap it off and just redo it again. Most important: have fun! This cake keeps for a few days if kept in the fridge and the lemon flavor will intensify.