Preheat oven to 350 degrees F. Grease a 9x5 inch loaf pan. I've tested with metal and cast iron.
In a large bowl, stir together the flour, bran, baking soda, baking powder, salt, and cinnamon.
In a mixing bowl, stir together the mashed bananas, coconut milk, maple syrup and oil.
Add the flour mixture to the coconut milk mixture and stir until blended. Stir in the walnuts.
Pour in the pan and bake on center rack for about 55 minutes.
Let cool completely.