Preheat oven to 350 degrees F (180 degrees C). Spray a 9 x 5-inch (2L) loaf pan with vegetable cooking spray.
In a small bowl, combine baking soda, baking powder and sour cream.
In a large mixing bowl, whisk egg, granulated and brown sugars and bananas. Stir in flour and ground flax, alternately with sour cream mixture, just until combined. Spread into prepared pan; top with pecans if using.
Bake for 50 to 60 minutes or until a tester inserted in centre comes out clean. Let cool in pan on rack for 10 minutes. Turn out onto rack to cool completely. Serve sliced banana bread spread with a tablespoon (15 mL) of NUTELLA(R).