Preheat oven to 350˚F. Line muffin pan with baking cups.
In medium bowl, combine flour, baking powder and salt; set aside. In large bowl, beat butter, sugar and peanut butter with electric mixer until smooth. Add eggs and vanilla; mix well. Alternately, add flour mixture and milk to butter mixture; mix well. Evenly distribute cupcake batter into baking cups.
Bake 22-24 minutes or until toothpick inserted into center comes out clean. Allow cupcakes to cool in pan on cooling rack for 5 minutes. Remove from pan; cool completely.