Heat oven to 350 degrees. Combine sugar and butter in large mixer bowl. Beat at medium speed, scraping bowl often, until creamy (2 to 3 minutes). Continue beating, adding eggs one at a time, until well mixed (2 to 3 minutes). Add sour cream, milk and vanilla. Continue beating, scraping bowl often, until well mixed (1 to 2 minutes). Reduce speed to low. Add flour; beat just until moistened. Spoon batter into greased and floured 12-cup bundt or 10-inch tube pan. Bake for 55 to 65 minutes or until toothpick inserted in center comes out clean. Cool 15 minutes; remove from pan. Cool completely. Sprinkle with powdered sugar, if desired.