1Preheat oven to 325 degrees. Move rack to middle of oven. Grease and flour a 10-cup bundt or tube pan.
Mix 3 types of sugar and butter with a mixer for 6 minutes on low speed. The mixture should be very light and fluffy with no visible sugar lumps. (This was a critical step.) Add eggs, beating well after each one. Scrape down the bowl, beat another minute and add vanilla. Add buttermilk and dry ingredients alternately, ending with buttermilk. Beat just until incorporated. It is important NOT to over beat the flour or it will get tough. Pour batter into prepared pan. Bake 60 to 75 minutes or until a wooden skewer comes out with just a bit of crumb. Cake will be brown on the outside but not burned-looking.
Cool 10 minutes in pan, then turn out on rack to cool.