6tablespoonsunsalted buttersoftened (I used margarine)
1/2cupfirmly packed brown sugar
Preheat oven to 350. Spray 8x2 or 9x2 inch pan with vegetable pan spray.
In small bowl, combine flour, baking powder, and salt. In large bowl, beat peanut butter, butter and sugars with electric mixer until light and fluffy.
Add eggs, one at a time, add vanilla; mix well. Add flour mixture, mix until well combined. Spread batter into prepared pan. Bake 30 -35 minutes or until toothpick inserted in center comes out clean. Cool completely before cutting.