Preheat the oven to 175°C fan-assisted.
Beat eggs and sugar well together.
Fold in flour, baking powder, vanilla sugar, and grated marzipan.
Spread the batter in a springform pan (about 24 cm in diameter) lined with parchment paper on the bottom and greased on the sides.
Remove the stones from the plums, cut them in half, and arrange them in a pattern on the tart.
Optionally, sprinkle with pearl sugar and chopped almonds/nuts.
Bake the cake at 175°C fan-assisted for 30-35 minutes, until it is golden and fully baked.
Serve the plum cake, preferably warm, with ice cream, whipped cream, or crème fraîche.