Set your oven to 350°F. Prepare a 9×5-inch loaf pan by coating it with cooking spray, butter, or by lining it with parchment for easier cleanup.
Place the mashed bananas in a large bowl. They should be very soft—this ensures the bread has plenty of natural sweetness and moisture.
Stir in the melted butter until fully combined. Add the sugar and mix until the batter looks uniform.
Add the eggs, one at a time, mixing well after each addition. Blend in the vanilla extract.
In a separate bowl, whisk the flour, baking soda, salt, cinnamon, and nutmeg together. This step helps the spices and leavening mix evenly into the batter.
Add the dry ingredients to the banana mixture gradually. Fold everything together gently—stop as soon as no streaks of flour remain.
If you want nuts in your loaf, fold them in now. (Toasting them first gives extra flavor, but it’s optional.)
Transfer the batter to your prepared pan and smooth out the top. Lightly tap the pan on the counter to release any large air pockets.
Bake for 55 to 65 minutes, or until a toothpick inserted in the center comes out clean or with a few moist crumbs.