I found this recipe in my Betty Crocker party cake book.
1 package yellow cake mix
1/3 cup water
1 cup peanut butter
2 eggs
preheat oven to 375

okay, I am not listing there directions because I did not follow them. Mix all ingredients together and then I used the pampered chef mix and chop instead of a fork on the top (no idea why but it worked great), sprinkle with sugar before baking
bake 10-12 minutes