Preheat oven to 325º

In a smaller mixing bowl, combine flour, baking powder, and salt together and set aside

In a larger mixing bowl, Cream peanut butter, butter, and sugar together until well combined, and somewhat lighter in appearance

Beat in eggs and vanilla, and beat together until fully incorporated

Stir in ⅓ of the flour mixture

Next, add milk, and mix until combined

Stir in remaining flour until fully combined

Pour into a greased 9x5 inch loaf pan and bake for about 75 minutes, until a toothpick inserted into the center comes out clean

Remove from oven and let rest 10 minutes

Loosen sides of loaf from pan, using a butterknife or icing spatula, and turn onto a wire cooling rack to finish cooling