Beat the warm butter, sugar and vanilla sugar in a mixing bowl until frothy. Add the eggs and stir in well. Mix the flour with the baking powder and stir into the mixture. Pour the batter into a prepared springform pan and smooth it out.
Mix the quark, eggs, sugar and vanilla sugar in a bowl. Add the poppy seed baking and stir into the quark mixture. Pour the quark and poppy seed mixture onto the batter and smooth it out.
Now make the crumble from the flour, sugar and the cold butter. This is best done by hand.
Peel the apples and remove the core. Now cut the apples into medium-sized cubes and distribute them on the quark-poppy-seed mixture. Finally, distribute the crumbles over the apple cubes.
Place the cake in the oven preheated to 170 degrees (top - bottom heat) and bake for about 60 minutes. After the baking time, take it out of the oven and let it cool down in the tin.