Preheat your oven to 350°F and grease a loaf pan or line it with parchment paper.
In a medium bowl, whisk together the flour, nutmeg, cinnamon, baking soda, and salt. Set aside.
In a large bowl, combine the mashed bananas, melted butter, sugar, egg, and vanilla. Mix until smooth.
Add the dry ingredients into the banana mixture and stir just until combined. Do not overmix.
Fold in the chopped walnuts.
Pour the batter into your prepared pan and smooth the top.
Bake for 55 to 60 minutes, or until a toothpick inserted in the center comes out clean.
Let the loaf cool in the pan for about 10 minutes before transferring it to a cooling rack.
