Wash, dry and stone the cherries, alternatively use drained sour cherries from the glass.
Separate the eggs, grate the chocolate or use chocolate shavings. Beat the egg whites with a pinch of salt until stiff.
Mix the butter with the sugar and vanilla sugar until frothy. Stir the egg yolks one after the other into the butter mixture. Add the chocolate and the ground hazelnuts and fold in the egg whites. (For those in a hurry: do not separate the eggs, but stir in slowly as a whole.)
Preheat the oven: 170 ° C top and bottom heat, 160 ° C convection. Line a 26 cm diameter springform pan with parchment paper.
Pour the batter into the mold and spread the cherries on it and bake on the lowest rack for about 1 hour.
Tip: easy to prepare, the next day it tastes even better!