Sift in flour in two batches and gently and slowly fold into the eggs until fully incorporated.
240 g flour, all-purpose
Layer bottom of 2 x 6 inch / 16 cm spring form pans or cake pans with parchment paper. Grease the edges of the pan with butter, and, preferably dust with flour. Remove the excess flour.
Divide butter in two and pour it into prepared cake pans.
In a separate bowl, mix blueberries with cornstarch and 1 tsp lemon juice.
400 g fresh blueberries, ½ tbsp cornstarch, 1 tbsp lemon juice
Evenly sprinkle blueberries in the cake pans.
Bake about 30-40 min until top is golden and inserted wooden skewer comes out clean. Don’t open the oven door for at least 30 minutes!
Cool the sponge in slightly open oven for 10 minutes.
Cool the sponge in the room temperature for 20 min, then release the edges of the pan or flip it upside down and remove parchment paper.
Let the cake sponges cool completely.
With the serrated knife or cake leveler cut every sponge in half.
Lemon Cream
Beat butter on high speed with a mixer, until it whitens and doubles in size, about 6 min
200 g butter, room temperature
Slowly add sugar, beating well between adding, so it incorporates well.
100 g icing sugar
Add lemon juice, vanilla and cream cheese and whip with a mixer just until combined.