Preheat oven to 350 degrees. Line a loaf pan with parchment paper so that there is an overhang on both sides of the pan.
Place the coconut oil in a small bowl. Microwave for 15-20 seconds until the coconut oil is melted.
Put the bananas in a mixing bowl and mash with a fork. Add the coconut oil and stir.
Add the sugar and vanilla, water, and vinegar, and mix until combined.
Add the gluten free flour, baking soda, baking powder, and salt and mix together.
Spoon into the prepared loaf pan*, and bake at 350 degrees for 40-45 minutes or until a toothpick inserted in the middle comes out clean.
Cool for 30 minutes in the pan, then remove from pan and cool on a cooling rack.
Once the loaf is fully cooled, use a serrated knife to slice it.
Notes
* I used a 9x5 loaf pan. If you use a narrower loaf pan, you may have to bake it longer to make sure it is done in the middle of the loaf.You can use up to ½ cup of oat flour in this recipe if you wish. If you use more than that, the recipe may become crumbly.I've made this recipe with many different combinations - part spelt flour, part oat flour, gluten free flour only, a mix of gluten free flour and oat flour, etc. It always turns out well!(Spelt flour is not gluten free, so it's not suitable for those on a gluten free diet).If you'd like a chocolatey treat, try adding ¾ cup of dairy free chocolate chips to this recipe.