Melt the butter for the bottom. Combine the ground almonds and xylitol and mix with the melted butter. Pour the base into a greased springform pan and press firmly.
For the topping, beat the cream until it is half stiff using a hand mixer. Then add the quark and eggs and mix well again. Then add the vanilla, the pudding powder, the xylitol and - if available - the zest of half a tonka bean to the mixture. Mix everything well again. Empty the finished mixture onto the almond base and spread the fresh blueberries on top (raspberries or currants also go very well).
Place the cake in the preheated oven and bake for about 50 minutes (don`t forget to test the chopsticks).