Wash the plums, cut in half and core. Separate the eggs and beat the egg whites with a pinch of salt until stiff. Put aside.

Mix the egg yolks with butter and powdered sugar for a few minutes with the hand mixer on the highest setting until creamy. Mix the flour, baking powder and cornstarch and stir in alternately with the egg liqueur on a low level. Finally, carefully fold in the egg whites.

Pour the dough into a greased springform pan (26 cm in diameter) lined with baking paper and smooth it out. Put the plum halves close together in the dough.

Bake in the preheated oven on the middle rack at 160 degrees convection for about 35 minutes.

Either dust the cooled cake with powdered sugar or cover it with an eggnog powdered sugar glaze.