Select the raspberries and mix with 1 teaspoon of flour. Cream fat, sugar, vanilla sugar and lemon peel. Stir in eggs one after the other. Add rum. Mix the remaining flour, starch and baking powder and finally stir into the fat mass.
Put some of the dough into a greased, breadcrumbed ring cake mould (approx. 2 litres capacity). Carefully fold the raspberries into the rest of the dough and put them into the mould as well. Bake in the preheated oven (electric cooker: 175°C/ gas: level 2) for approx. 50 minutes.
Let the finished cake rest in the mould for about 15 minutes, then turn out of the mould and let it cool down on a cake rack. Dust with icing sugar and serve decorated as desired with raspberries and lemon balm.