Add 75 grams of sugar to the yolks and beat with a mixer at maximum speed until thick, almost white.
Wash and dry the beaters and beat the whites at maximum speed until the mixture becomes white and thick. The mixer attachments should leave a clear trail. Only now pour in the remaining sugar and continue beating until the mixture becomes snow-white and shiny.
Add the yolks to the whites and mix very carefully with a spoon until the mixture becomes uniform and light yellow in color.
Add flour and mix. Do not mix for too long, as the dough may become too compact and lose its airiness.
Once the lumps of flour have disappeared, transfer the dough into the pan, smooth the surface and place in a preheated oven for 30-35 minutes.
Prepare the cream. Mix sour cream with sugar. Using a mixer, beat the sour cream with two types of sugar until completely dissolved.
Beat the cottage cheese with a blender and mix it thoroughly with sour cream. Put the finished mixture in the refrigerator for 30 minutes.
Remove the sponge cake from the pan when it has cooled completely. The butter will cause the sponge cake to stick to the sides of the pan and will not settle when it cools. Carefully run a knife along the sides and separate the sponge cake.
Assemble the cake. Cut the sponge cake into 2 parts and spread the prepared cream. For better soaking, grease the edges of the cake. Decorate the top of the cake with sugared apples and leave the cake in the refrigerator for a few hours so that the cream thickens and the sponge cake soaks.