Preparation:
1. First, put the sugar and vanilla sugar in a bowl and whisk the eggs.
Then mix the baking powder with the flour and gradually add it to the eggs. Continue stirring. Now add the melted butter and stir.
2. Next, peel and dice the apples, grease the baking pan, and add the apples (sprinkle with sugar or cinnamon if desired). Pour the batter over the apples and smooth the surface.
3. Now place in a preheated oven at 180 degrees Celsius (350 degrees Fahrenheit) and bake for 40–45 minutes (baking time may vary; test with a toothpick before removing the cake from the oven). Finally, sprinkle the finished cake with powdered sugar.