Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan.
In a large mixing bowl, combine the mashed bananas and melted coconut oil. Mix until well combined.
Stir in the brown sugar, beaten egg, and vanilla extract until smooth.
Sprinkle the baking soda and salt over the mixture, then add the ground cinnamon. Mix well.
Gradually fold in the all-purpose flour until just combined. Be careful not to overmix. If using, fold in the chopped nuts.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Allow the banana bread to cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely.