Preheat oven to 350 degrees. Spray a standard sized loaf pan with nonstick spray and set aside.
In a medium bowl, combine flour, baking soda, baking powder and salt.
In large bowl, with a stand mixer or hand mixer, beat bananas, eggs, butter and sugar and extract. Add dry ingredients to wet ingredients and mix until combined.
Melt Nutella in microwave for approximately 20 seconds to soften slightly.
Pour half the banana bread batter into the loaf pan. Using ½ cup Nutella, dollop spoonfuls on top of batter, swirl with a knife. Pour the rest of the banana bread batter on top and repeat swirl process with the rest of the Nutella.
Bake for 50 minutes or until toothpick inserted to center comes out clean. Let cool in pan for 10 minutes then remove to cool the rest on a backing rack.