Preheat oven to 325º. Bake in tube pan.
In mixer bowl, combine butter, sugar, brown sugar, peanut butter; blend well.
Add eggs; mix well.
Sift dry ingredients: flour, baking powder, salt and baking soda.
Alternate adding dry ingredients and milk to other ingredients in mixer bowl; add vanilla; blend well.
Pour batter into tube pan.
Bake in 325º oven for 1-1/2 hours.
In mixer bowl, cream together all ingredients; pour over cake.