Preheat oven to 325 degrees F
Grease and flour a tube pan
Cream butter and sugar until fluffy
Add eggs yolks (reserve egg whites). Beat until light.
Add all the remaining ingredients.
Beat egg whites in a separate bowl until stiff and fold by hand into batter.
Pour into the greased and floured tube pan
Bake 325 for about an hour, until a toothpick comes out clean
While the cake is baking make the buttermilk sauce