Preheat oven to 350 degrees. Grease a loaf pan and set aside.
Combine butter, fruit butter, maple syrup and egg together. Beat with a wooden spoon or a hand mixer. Stir in mashed bananas and maple extract. Set aside.
In a small bowl, whisk the flours together with baking soda, baking powder and salt.
Add the dry ingredients to the wet ingredients in thirds, each time mixing to fully integrate before adding more. Stir toasted walnuts into the batter.
Pour batter into greased loaf pan and bake for 50-55 minutes, until a toothpick comes out mostly clean.