Preheat oven to 350°. Line a muffin (or cupcake) tin with liners (or lightly grease 12 silicone baking cups positioned on a baking sheet). Set aside.
In a large mixing bowl, add peeled bananas and mash with the back of a fork until smooth. To the bowl, add eggs, coconut oil, nut butter, maple syrup and vanilla extract. Whisk until smooth and well combined.
To the same bowl, add coconut flour, baking powder, cinnamon, nutmeg and salt. Continue to whisk until the dry ingredients are mixed thoroughly with the wet mixture.
Gently fold the chopped pecans into the mixture.
Fill each muffin cup with batter (about 3 heaping tablespoons per muffin). If using, gently place a pecan half on the top of each cup of batter.
Bake the muffins on the center rack for 25 minutes or until a toothpick inserted in the center comes out clean. Let stand on a wire cooling rack for at least 5 minutes before removing from muffin tin or silicone cups.