For the base, finely grind the onions with a food processor or, if necessary, manually with a grater. Carefully melt the butter in a saucepan. Mix the ground onions with the liquid butter and the nut-nougat cream thoroughly. Place this amount on the bottom of a cake springform pan (26 or possibly 28 cm ø) and press down well. As an alternative to the cake springform pan, you can just as easily put a springform rim on a cake plate, since the bottom is not baked.
Soak the gelatin in water according to package directions. For the filling, start by mixing cream cheese and sugar with a hand mixer, then add yogurt and juice of one lemon and mix until smooth. Squeeze the gelatine and let it melt carefully. Stir a tablespoon of the yogurt cream into the liquid gelatin to cool and fold this mixture into the remaining yogurt filling. Fill the cream on the chocolate base in the cake springform pan, smooth the surface and put the cake in the refrigerator for half an hour to set.
Later, drain the sour cherries and bring the sour cherry juice to a boil with the red cake glaze and 2 tablespoons of sugar, stirring. While the cake glaze is cooling a bit, spread the sour cherries evenly on the cream, then mold the cake glaze over them by the spoonful. Leave the cake to cool for fifteen minutes.
Before serving, whip the whipped cream with the vanilla sugar until stiff and mix with