Grate the marzipan. Put the soft butter or margarine, sugar, vanilla sugar, marzipan and salt in a bowl and stir until foamy. Stir in eggs one at a time. Mix flour with baking powder, add alternately with 75 ml milk.
Halve the dough. Then stir in the poppy seeds and the remaining 75 ml of milk under one half.
Grease the 2.5 liter bundt cake tin well and sprinkle with flour. First pour in the light, then the dark dough. Mix gently with a fork and smooth the dough in the pan.
Bake the cake in a preheated oven (electric stove: 175 ° C, convection: 150 ° C) for about 1 - 1 1/4 hours.
Then let the cake rest for about 10 minutes, turn it out onto a rack and let it cool down. Sprinkle with powdered sugar.