Beat the butter and sugar until frothy. Stir in one egg yolk at a time. Fold in the grated poppy seeds, flour and rum. Beat the egg whites and salt into snow and fold into the poppy seed mixture.
Pour the dough into a greased springform pan (26-28 cm). Bake in the preheated oven at 160 - 180 ° C for about 60 minutes. After cooling, sprinkle with icing sugar.
Whipped cream or caramelized pears go very well with this.