Beat the eggs with the sugar until frothy. Mix the flour, baking powder, vanilla sugar and salt with the cocoa and fold into the egg mixture. Then stir in the quark and grated orange and pour into the greased springform pan (24 cm) dusted with flour.
Bake in the preheated oven on the 2nd rack from the bottom at 200 ° C for approx. 20 - 25 minutes. Let the cake cool down and dust with powdered sugar if you like. A quark-vanilla yoghurt cream tastes very good with it.