Grate marzipan. Puree sour cream, marzipan, 3 eggs, 75 g sugar and sauce powder. Wash, halve and stone the plums. For the dough mix flour, 75 g sugar, salt and baking powder. Add 1 egg, quark, milk and oil, knead to a smooth dough with the dough hooks of the hand mixer. Roll out the dough rectangularly (approx. 35 x 22 cm) on a floured work surface. Fold a piece of aluminium foil long enough to form a stable strip.
Place the aluminium strip in the middle of a fat pan and press it firmly. Line half a baking tray with the dough and cover it tightly with plum halves. Pour the marzipan icing on top and bake in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 25-35 minutes. Remove the cake from the oven and let it cool down on a cake rack. Roast the flaked almonds on a tray in the oven at residual heat. Cut the cake into pieces, sprinkle with almond flakes