Clean, wash, drain, halve and stone the plums. Wash lemon, grate dry and grate peel. Halve lemon, squeeze juice. Mix crème fraîche, vanilla pulp and 4 eggs.
Coarsely grate the marzipan. Cream butter, sugar and marzipan with the whisk of the hand mixer. Stir in 6 eggs one after the other. Stir in lemon zest and juice. Mix flour, starch and baking powder and stir into the fat-egg mixture.
Spread the dough into a deep, greased baking tray (36 x 41 cm; 3 cm high) that has been dusted with flour. Spread the plums on top and pour the icing over it. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see
manufacturer) bake for about 40 minutes, take out and let cool on a cake rack. Before serving, dust with icing sugar and cut into pieces. Serve with whipped cream and plum jam.