1. Preheat oven to 350 degrees Fahrenheit.
2. In a small saucepan on a low flame, heat the butter until melted.
3. In the bowl of an electric mixer, cream the eggs and the sugar until creamy. Add sour cream, vanilla sugar and baking powder.
4. Meanwhile, remove the butter from heat and cool slightly. Add to mixture. Add flour and mix well.
5. The batter will be very thick; use the 1/4 cup milk to thin it out.
6. Grease a 10-inch tube or Bundt pan with butter and fill with batter.
7. Bake for 1 hour and 5 minutes. Check for readiness by inserting a skewer or a knife into the center of the cake.