A great cake recipe for any occasion:
Preheat the oven to 190 o C. Cream the butter with the sugar, orange zest, salt and vanilla sugar. Add the eggs one by one and fold them in. Always add a new egg when the previous one is fully incorporated.
Sift the flour and mix with the baking powder. Stir the flour-baking powder mixture into the cake mixture one tablespoon at a time. Finally, mix in the orange liqueur.
Spread a loaf pan thinly with butter and dust with flour. Pour the mixture into the pan, smooth it out and bake the cake on the lowest rack in the oven for about 55 minutes. After 1/2 hour, cover the top of the cake with parchment paper. After about 50 min. of baking time, test the cake for doneness.
Remove the cake from the heat, cool in the pan for a quarter of an hour. Now slide out of the pan and place on a rack to cool. Dust the surface, each to taste, with powdered sugar.