Preheat the oven to 180 degrees top / bottom heat. Grease and flour a small bundt pan (18 cm).
Beat the egg whites with a pinch of salt and 25 g of sugar until very stiff.
Mix the butter with the remaining 50 g sugar and the tonka bean zest until frothy. Mix the flour and baking powder and briefly stir in with eggnog and milk. Finally fold in the egg whites (first a third, then the remaining two thirds).
Pour the dough into the prepared Gugelhupf pan and bake for about 40-45 minutes. Chopstick sample!
After cooling, cover the Gugelhupf with cake icing.
Tip: Double the amount is suitable for a normal-sized Gugelhupf pan. The baking time must be increased to approx. 50-55 minutes.