First separate the eggs. Beat the egg whites with a little lemon juice until stiff. Mix egg yolks, powdered sugar, vanilla sugar and bitter almond flavoring until foamy. Stir in almonds and rum.
Fold in flour and beaten egg whites alternately. Spread the sponge mixture on a baking sheet lined with baking paper. Bake at 180 °C for approx. 10 minutes.
Coat the still hot sponge cake dough with Powidl and roll it up.