Beat the butter with the sugar and 1 sachet of vanilla sugar until creamy, then stir in the egg yolks and custard powder. Add the quark and stir well again. Beat the egg whites until stiff and fold in.
Grease a 26 cm springform pan and pour in the mixture and smooth it out. Preheat the oven to 150 degrees and bake the cake for 1 hour.
Then leave in the form. Drain the sour cherries well and place on the cooled cake. Mix the sour cream with 2 sachets of vanilla sugar and heat lukewarm in the microwave so that the sour cream becomes a little smoother. Then spread over the cherries. Finally mix a little sugar with cinnamon and sprinkle over the cake.
When everything has cooled down, the cake can be removed from the mold.