Preheat oven to 350 degrees F. Coat a 9×5 loaf pan with cooking spray and set aside. Using a stand mixer fitted with the paddle attachment (or a large mixing bowl with a hand mixer), combine the butter, brown sugar, sugar, eggs and vanilla and beat until combined.
In a separate bowl, combine the flour, baking powder, baking soda and salt. Mix well. Gradually add to the butter mixture and beat on medium-low speed until just combined. Stir in the bananas and chopped Reese’s peanut butter cups.
Pour the batter into the prepared pan, spreading in an even layer. Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center comes out clean. Let sit in the pan for 10 minutes before removing and serving.