Put the flour in a bowl, make a depression in the middle and crumble the yeast into it. Heat 100 ml milk and add it to the yeast with 30 g sugar. Mix it with some flour from the edge to a thick mash and let it rise covered in a warm place for about 15 minutes.
Melt 80 g fat, add the remaining milk. Add the egg, lukewarm fat mixture, 70 g sugar and lemon zest to the pre-dough. Knead well with the dough hooks of the hand mixer, cover and leave to rise for another 30 minutes.
In the meantime, wash the plums and drain them well. Halve the plums and remove the stone. Roll out approx. half of the dough on a greased, flour-dusted fat pan (35x38 cm), cover and leave to rise for 10-15 minutes.
Roll out remaining dough to the size of the baking tray and dust with flour. Cover dough with plums in the fat pan. Mix 25 g sugar and cinnamon and sprinkle over the plums. Carefully fold the remaining dough and cover the plums with it.
Press the edges and press hollows into the dough. Mix almonds, remaining sugar (50-75 g) and vanillin sugar and sprinkle on the cake. Spread the remaining fat in flakes on top. Bake in the preheated oven (electric: 200 °C/ gas: level 3) for about 30 minutes.
Leave the cake to cool on the tray and cut it into about 20 pieces. Serve with whipped cream.