Mix the butter with 125 g sugar, 1 pinch of salt and 1 piece of vanilla sugar in a mixing bowl with a hand mixer until creamy.
Stir in the egg yolks one at a time.
Mix the flour and baking powder and stir in quickly alternately with the milk.
Fill half of the dough into a springform pan (26 cm) and smooth it out.
Beat the egg whites until stiff and slowly pour in 200 g of sugar.
Keep beating until the sugar has dissolved.
Spread half of the egg whites on the dough in the pan.
Sprinkle with half of the almond flakes and bake in the preheated oven at 150 ° for 25 - 30 minutes.
Let it cool down, remove it from the mold and let it cool completely.
Do the same with the other half of the dough, egg whites and flaked almonds.
Detach this base from the edge of the springform pan and put it back in.
In the meantime, clean and wash the rhubarb and cut into small pieces.
Bring to the boil with 100 ml of cherry nectar and 4 - 5 tablespoons of sugar, cover and simmer for approx. 5 minutes.
Mix the custard powder with 6 tbsp cherry nectar until smooth.
Stir in the rhubarb and simmer for about 1 minute.
Let cool down a bit and spread the compote evenly on the cake base and put the pan in a cold place.
Whip the cream until stiff, pour in 2 pieces of vanilla sugar.
Spread the cream on the cooled compote, place the second cake base on top.
Chill until ready to serve.