Preheat oven to 350°F. Spray two 9x5" loaf pans with cooking spray.
In a medium bowl, whisk the flour, salt, and baking powder. In a larger bowl, mix bananas, butter, sugar, peanut butter, eggs, and milk until well combined. Add the dry ingredients, in batches, to the wet ingredients stirring just until combined.
Pour the batter in the prepared the prepared pans. Bake for approximatley 50 minutes to 1 hour. Use a skewer or cake tester to check it's baked through. Let it cool in the pan for 15 minutes before transferring to a wire rack.
Notes
The bread will keep well at room temperature for several days or up to a week in the refrigerator. You can also freeze the loaves for up to three months.