Preheat the oven to 350ºF. In a large bowl, whisk together the flour, baking powder and salt. Set aside. In a stand or with a hand held mixer, mix together the butter, brown sugar and eggs until well combined.
Slowly add the flour mixture and the mashed bananas alternatively until mixed well. Fold in the blueberries and macadamia nuts. Lightly spray a loaf pan with non-stick cooking spray. Then line the pan with parchment paper and lightly spray it again.
Spread the batter evenly in the loaf pan. Bake in the oven for 1 hour or until a toothpick inserted in the center pulls out clean. Remove from the pan and cool on a rack.
Notes: I like to heat up a slice and place a pat of butter on top. Goes great with the morning coffee.