Preheat your oven to 350°F (175°C). Grease an 8x4-inch loaf pan or line it with parchment paper. Chop the walnuts and set aside.
In a medium bowl, sift together the flour, baking powder, baking soda, nutmeg, and salt. Set aside.
In a large bowl, mash the peeled bananas thoroughly with a fork or potato masher until mostly smooth. Small chunks are fine, but no large pieces.
Add the coconut sugar and melted coconut oil to the mashed bananas. Mix until evenly combined.
Add the dry ingredients to the banana mixture. Gently fold everything together with a spatula just until combined - do not overmix.
Fold in the chopped walnuts (or your preferred mix-in).
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake at 350°F for 50–60 minutes for a single 8x4-inch loaf, or 30–40 minutes for mini loaves.
Test doneness by inserting a toothpick into the center. It should come out clean or with a few dry crumbs. If batter clings, bake in 5–8 minute intervals until done.
Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.