1. Preheat oven to 350°F. Grease a 9x5 loaf pan.
2. Cream the butter, sugar until smooth. Add the eggs and yolk; blend well. Add the banana, then the quinoa; blend well.
3. In another bowl, mix the flour, baking soda and salt together. Add the flour mixture to the banana mixture and stir until all incorporated. Add nuts. Pour into prepared pan.
4. Bake 1 hour or until knife inserted in the center comes out clean.