Mix the sugar, vanilla sugar and butter until frothy. Mix in the eggs.
Mix flour, cornstarch and baking powder and stir in briefly (add milk if necessary).
Spread half of the batter on a small baking sheet lined with parchment paper.
Mix the rest with cocoa powder and a little milk and spread over it. Spread the drained cherries on the batter and press in. (Keep the juice of the cherries!)
Bake for about 25 minutes at 175 degrees. (Preheat the oven.)
Mix the quark and galetta, spread evenly on the cooled cake. Score a wave pattern with the fork. Prepare the juice of the cherries with the cake glaze according to the instructions on the package, allow to cool for 1-2 minutes and spread over the quark mixture.