Grease a springform pan (26 cm Ø). Separate the eggs. Cream the fat, 125 g sugar, 1 pinch of salt and 1 vanilla sugar with the whisks of the hand mixer. Stir in the egg yolks one by one. Mix flour and baking powder and stir in briefly, alternating with the milk. Fill half the dough into the form and smooth it down.
Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2). Beat the egg white until stiff, sprinkle 200 g sugar into the mixture. Continue beating until the sugar has dissolved. Spread half the beaten egg whites on the dough in the mould. Sprinkle 2 tbsp. flaked almonds over the top. Bake in a hot oven for 25-30 minutes. Leave to cool, remove from the tin and let cool completely, then fill the rest of the dough, beaten egg white and flaked almonds into the tin and bake. Let it cool down.
In the meantime, clean, wash and cut the rhubarb into small pieces. Bring to the boil with 100 ml water and 4-5 tbsp sugar, cover and simmer for about 5 minutes. Stir pudding powder and 6 tbsp. water until smooth. Stir into the rhubarb, bring to the boil again and simmer for about 1 minute while stirring. Allow to cool slightly, spread evenly on a cake base and chill.
Whip the cream until stiff, pour in 2 vanilla sugars. Spread on the cooled compote, place the second cake base on top and dust with icing sugar.