In large bowl, beat butter and sugar with electric mixer on high speed until creamy. Add eggs, one at a time, beating well after each addition; set aside. Stir buttermilk and vanilla into coffee mixture. Starting with flour mixture, alternately beat flour mixture, 1/3 at a time, and coffee mixture, 1/3 at a time, into butter mixture on medium speed, scraping bowl occasionally. When all ingredients have been added, beat 30 to 60 seconds longer or until batter is smooth and well blended. Pour into pans.