Grease the spring plate (28 cm Ø) or spring form. Knead 150 g flour, 100 g sugar, 1 vanillin sugar, 1 pinch of salt and 125 g butter in flakes first with a hand mixer, then briefly with your hands to form crumbles
Clean and wash the rhubarb and cut it into pieces about 1 cm wide. Coarsely grate marzipan. Mix with 150 g butter, 125 g sugar, 1 vanillin sugar and 1 pinch of salt until creamy. Stir in the eggs one by one. Mix 250 g flour and baking powder and stir in briefly, alternating with the milk
Spread the sponge mixture into the mould. Mix crème fraîche, sauce powder and 2 tablespoons icing sugar briefly. Mix with rhubarb. Spread on the dough. Sprinkle the crumbles on top and grate between your fingers. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/ gas: level 2) for 1-1¼ hours. Let cool off. Sprinkle the cake with icing and decorating sugar