- Preheat oven to 350 degrees F. Grease and flour a 8x8 inch pan.
- Sift together the flour, baking powder and salt. Set aside.
- In a large bowl, cream together the peanut butter, butter and brown sugar until light and fluffy.
- Beat in the eggs one at a time, then stir in vanilla.
- Beat in the flour mixture alternately with the milk, mixing just until incorporated.
- Pour batter into prepared pan.
- Bake in the preheated oven for 35-45 minutes, or until a toothpick inserted into the center of the cake comes out clean.
- Allow to cool in pan.