From Tea Time at the Masters, by the Junior League of Augusta, Georgia
1 cup butter softened to room temperature
2 2/3 cups sugar
¼ teaspoon baking soda
6 ounces sour cream
3 cups flour
1 teaspoon vanilla
Cream butter and sugar well in a mixing bowl or with an electric mixer. Add one egg at a time, mixing well after each addition. Stir baking soda into sour cream, stirring it in to dissolve. Add flour and sour cream to butter mixture. Add vanilla.
Pour into a greased and floured tube or bundt pan. Bake at 300 degrees for 1 hour (place the cake in a cold oven, and then set the temperature. While baking, do not open oven). Continue baking at 325 degrees for 15 minutes longer.
Cool on a rack for 10 to 15 minutes, then remove to a plate or cooling rack.