Pour the blueberries into a colander and let them drain.
Mix the sugar with the egg, milk and oil. Add flour, baking powder and quark and mix everything briefly. Now it`s best to knead the dough with your hands and then press the dough onto a greased tray. Spread the blueberries on top. Knead the crumble from the butter, sugar and flour and sprinkle evenly over the blueberries.
Bake at 200 degrees on the middle rack for about 30 minutes. Sprinkle the vanilla sugar on the hot cake.
This cake can also be prepared with plums, sour cherries or other fruit.