Mix egg and sugar in a bowl. Add melted butter and 2 tablespoons of kefir, mix a pinch of salt. Add flour with baking powder and knead the dough. Place the dough in the refrigerator for 30 minutes. Stuffing – add eggs, starch, sugar, vanillin to the cottage cheese and pierce with a blender. Grate apples on a coarse grater. Roll out the dough into a layer and put in a mold. lay out apples with blueberries, then a layer of cottage cheese and again berries. Bake at 180 degrees for 45-50 minutes.