Mix the yolks, sugar, vanilla sugar and butter until frothy. Mix the flour and baking powder and stir in. Fold in the egg whites.
Spread the dough on a baking sheet lined with baking paper and top with any fruit. I personally prefer apricots or plums (for non-Austrians: apricots or plums),
but have also eaten it with cherries.
Bake at 190 ° C top / bottom heat for approx. 25 - 35 minutes until the surface is golden brown. After cooling, sprinkle with powdered sugar.
The cake is really THE best seller because it stays uniquely juicy. There is hardly anyone who has tried it and not immediately asked for the recipe.