Beat butter at medium speed with electric mixer about 2 minutes or until soft
Gradually add sugars, beating at medium speed 5 to 7 minutes. Add eggs,
one at a time, beating just until yellow disappears.
Combine flour, baking soda and cocoa; add to creamed mixture alternately with
sour cream, beginning and ending with flour mixture. Mix at lowest speed just until
blended after each addition; stir in vanilla extract.
Spoon batter into greased and floured 10-inch tube pan.
Bake at 325 degrees F for 1 hour and 20 minutes or until a wooden pick inserted
in center comes out clean.
Cool in pan on wire rack 10 to 15 minutes; remove from pan, and cool completely
on wire rack.