Grate marzipan. Knead 100 g marzipan, 100 g butter, 75 g sugar and 150 g flour with the dough hooks of the hand mixer into crumbles and chill. Wash, halve and stone the plums. Mix 125 g butter, 100 g sugar, 100 g marzipan and vanilla sugar with the whisks of the hand mixer until smooth and creamy. Stir in the eggs one by one. Mix 200 g flour and baking powder and stir in alternately with the buttermilk.
Put the dough into a square springform pan (23 x 23 cm) greased and sprinkled with flour and smooth it down. Put plums on the dough and spread the crumbles on top. Bake in the middle of the preheated oven (electric oven: 175 °C/ convection oven: 150 °C/ gas mark 2) for 30-40 minutes. Remove the cake and let it cool down on a cake rack. Dust with icing sugar before serving. Whipped cream tastes good with it
Waiting time 1 hour