Preheat the oven to 170 °C for the apricot cake with marzipan. Mix flour with baking powder and cornstarch. Separate the eggs and beat the egg whites with salt until creamy.
Beat the yolks with the butter, sugar, vanilla sugar and marzipan until very creamy, then fold in the flour and beaten egg whites alternately. Grease a square baking pan with butter and dust with flour, pour in the dough and smooth it down.
Cut apricots in half, remove seeds and place tightly on the dough. Bake in the preheated oven for about 45 minutes.
When cooled, cut the apricot cake with marzipan into pieces and sprinkle with sugar.