Cut butter into pieces. Knead flour, butter, sugar, sour cream, rum and egg with the dough hooks of the hand mixer, then work into a smooth dough with your hands. Wrap the dough in foil and chill for about 30 minutes. Roll out the dough on a floured work surface to a thin rectangular shape about 2 mm thick. Cut strips (10 x 4 cm) with a serrated dough wheel.
Cut an approx. 6 cm long slit in the middle of each strip. Pull one end of the strip through the slit to a skipper's knot. Heat frying fat in a pot. Fry the apron cake in it for 3-4 minutes and let it drip off on kitchen paper. Knead the dough again and process in the same way. Wash lemon and orange and rub dry. Tear off small pieces of both fruits with a pestle ripper. Halve the lemon and squeeze 1 half. Stir 2 tablespoons of juice and 100 g icing sugar until smooth.
Wash lemon and orange and rub dry. Tear off small pieces of both fruits with a pestle ripper. Halve the lemon and squeeze 1 half. Stir 2 tablespoons of juice and 100 g icing sugar until smooth. Spread half of the cold apron cake with the icing and sprinkle with a few small pieces immediately. Dust the other half with approx. 2 tablespoons icing sugar