1. Heat oven to 325°F. Grease and flour 12-cup fluted tube pan or 10-inch tube pan.
2. Beat butter, sugar and vanilla in large bowl 3 minutes on medium speed of mixer. Add eggs, one at a time, beating well after each addition. Stir together flour, cocoa, baking powder and salt; add alternately with buttermilk to butter mixture, beating well just until blended. Pour into prepared pan.
3. Bake 1 hour and 20 minutes or until wooden pick inserted in center comes out clean. Cool 10 minutes; remove from pan. Cool completely.
4. Sprinkle with powdered sugar or glaze with VANILLA GLAZE or BUTTER RUM GLAZE. Garnish with pecans or walnut halves, if desired. Makes 12 servings.
VANILLA GLAZE: Melt 1/3 cup butter or margarine in small saucepan. Remove from heat; stir in 2 cups powdered sugar and 1-1/2 teaspoons vanilla extract. Add 2 to 3 tablespoons water, 1 tablespoon at a time, beating with whisk until glaze is of desired consistency. Spoon onto cake allowing some to drizzle down sides.
BUTTER RUM GLAZE: Omit vanilla; substitute 2 tablespoons light rum or 1 teaspoon rum flavoring. Stir in hot water, 1 teaspoon at a time, until glaze is of desired consistency.
* Use 1 tablespoon and 1-1/2 teaspoons white vinegar plus milk to equal 1-1/2 cups.
NOTE: Two 9x5x3-inch loaf pans may be substituted for tube pan. Bake at 350°F. 1 hour and 10 minutes.