Wash the plums, dab dry, cut in half and remove stones. Cream 125 g fat, 100 g sugar, vanilla sugar, salt and 1 teaspoon cinnamon with the whisk of the hand mixer. Stir in the eggs one after the other. Mix flour, starch and baking powder, add to the fat-egg mixture with the milk and stir in evenly. Grease a springform pan (26 cm Ø), add the dough and smooth it down.
Spread plum halves on top. Spread 20 g butter as flakes on the cake. Mix 2 tablespoons of sugar with 1 teaspoon of cinnamon, sprinkle over it and bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 35-40 minutes. Let the cake cool down on a cake rack, remove from the tin and dust with icing sugar. Serve with vanilla quark, refined with whipped cream