Wash the plums, drain, halve and stone them. Mix egg yolks, 200 g sugar and cinnamon well with a fork. Whisk the fat, salt, vanillin sugar and 150 g sugar with the whisk of the hand mixer until white-creamy. Stir in the eggs one after the other. Mix flour, starch and baking powder, stir in briefly
Place the dough on a greased, floured fat pan of the oven (32 x 39 cm), smooth it down. Spread plums evenly and loosely on top. Pour egg yolk-sugar mixture over it. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: see manufacturer) for approx. 50 minutes
Remove from the oven, place on a cake rack and allow to cool. Cut into pieces and serve. Serve with whipped cream sprinkled with cinnamon sugar