1Preheat oven to 350, Combine cola and buttermilk in a 2 cup measuring cup.
2Beat butter with a electric mixer at low speed until creamy, Gradually add sugar,until well blended, add eggs and vanilla beat a low speed until well blended.
3Combine flour and next 2 ingredients in a medium bowl. Add to butter mixture alternately with cola mixture, beginning and ending with flour mixture. Beat at low speed just until blended after each addition. Pour batter into a lightly greased 13x9 inch pan.
4Bake at 350 for 30 t0 35 minutes or until wooden pick inserted in center comes out clean. Cool on rack in pan for 10 minutes.
5Meanwhle, prepare Peanut Butter Frosting. Pour over warm cake. You can sprinkle with chopped p-nuts if you desire this is optional.
6PEANUT BUTTER FROSTING.
Melt butter in a large saucepan over medium heat. Whisk in milk, and bring to a boil, whisking constantly. Reduce heat ot low, and whisk in peanut butter until smooth. Gradually whisk in sugar until smooth; remove from heat, and whisk in vanilla. USE IMMEDIATLEY POUR OVER WARM CAKE.