Preheat oven to 350°F and grease a loaf pan.
Mash bananas in a large mixing bowl until mostly smooth.
Stir in melted coconut oil, sugar, milk, and vanilla until combined.
Add baking soda, baking powder, cinnamon, and salt. Mix well.
Fold in the gluten-free flour blend until just incorporated. Do not overmix.
Stir in nuts if using, then pour batter into the loaf pan.
Bake for 45 to 55 minutes or until a toothpick comes out clean.
Cool slightly before slicing and serving.