For the dough, mix the quark, oil, egg, milk, sugar, salt and vanilla sugar together. Mix the flour with the baking powder and knead in.
Peel the apples, cut out the core and cut into wedges.
Roll out the dough in a 28 cm springform pan and cover with the apple wedges.
For the crumble, quickly knead the softened butter with the sugar, cinnamon and flour to form a dough and crumble with your hands. Spread the crumble on the cake and bake the whole thing at 200 ° C for about 30 minutes.