Preheat oven to 350 degrees F. Grease and flour 12 cup fluted tube pan. Beat butter, sugar, eggs and vanilla in large bowl until light and fluffy; stir in sour cream. Stir together flour, cocoa and salt. Stir baking soda into buttermilk in med. bowl; add alternately with dry ingredients to butter mixture. Beat 2 minutes.
Pour batter into prepared pan.
Bake 50 minutes or until wooden pick inserted into center comes out clean. Cool in pan 10 minutes. Remove from pan to wire rack; cool completely. Glaze with Orange Glaze; garnish as desired.
ORANGE GLAZE: Combine powdered sugar, melted butter or margarine, orange juice, vanilla and orange peel; beat until smooth.