Mix cocoa and 200 ml hot water to a creamy mixture. Separate the eggs. Beat the egg white in 3 portions until stiff. Add 2 tablespoons of sugar to each portion. Continue beating until the sugar has dissolved.
Beat the egg yolks, 300 g sugar and vanillin sugar in a large bowl for about 7 minutes until creamy. Briefly stir in the quark, pudding powder and lemon zest. Stir the cocoa mass into 1/3 of the cheese cream. Fold in 1 portion of beaten egg white. Fold 2 portions of beaten egg white into the light cheese mixture. Spread the dough in strips on a greased, breadcrumbed pan of the oven. Spoon lightly into each other. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: not suitable/ gas: level 2) for approx. 1 hour. Open the oven door.
Spread the dough in strips on a greased, breadcrumbed pan of the oven. Spoon lightly into each other. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: not suitable/ gas: level 2) for approx. 1 hour. Open the oven door. Leave the cake to stand for another 20 minutes. Serve completely cooled down