Preheat the oven to 350°F and oil a loaf pan.
Mash the 3 bananas thoroughly in a medium mixing bowl. There can be a few chunks, but you want them to mostly be a smooth, thick paste.
Beat the sugar into the bananas. Then, add the eggs, oil, and vanilla and mix them in thoroughly.
In a separate bowl, combine the flour, baking soda and powder, salt, cinnamon, and nutmeg. Whisk them together until they are well mixed.
Add the dry ingredients to the wet and stir until they are combined. Add about 2⁄3 of the walnuts and pecans (or just walnuts if that’s what you’re using) and continue stirring until the batter is well mixed and there are no streaks of flour left.
Spread the banana bread batter in the greased loaf pan and sprinkle the top with the remaining nuts.
Bake the banana bread for 50 minutes to 1 hour, or until a toothpick inserted in the center comes out clean.
Allow the bread to cool in the pan for a few minutes, then turn it out on a cooling rack and let it cool completely.