Whisk melted butter, eggs, kefir and vanilla sugar in a deep bowl.
Add flour, soda and powdered sugar to the mixture. Stir until smooth.
Peel and slice the apples.
Grease a baking dish with butter, shift half of the dough, then spread the apples. Cover with the remaining dough and bake at 180 degrees for 40 minutes.
Cool the cake, remove from the mold and serve.
Pie with apples on kefir is very simple and quick to prepare, the cake is very tender, airy and aromatic. This cake is perfect for family tea drinking, sweet or sour apples are suitable for cooking, if you take sweet apples then sugar can not be added to the dough.