Preheat the oven to 180 degrees C. Line a loaf pan with parchment paper or vegan butter spread.
Place coconut oil in a small bowl. Microwave for 15-20 seconds until coconut oil is melted. Alternatively, you can heat up the oil on the stove.
Place the bananas in a mixing bowl and mash with a fork. Add the coconut oil in and stir.
Add the sugar and vanilla, water and vinegar. Mix.
Add the gluten free flour, baking soda, baking powder, walnuts and salt to the mixture. Mix.
Spoon into the loaf pan and bake at 180 degrees C for 40-45 minutes.
Cool for 30 minutes in the pan, then remove from pan and cool on a cooling rack.
Once cooled, use a serrated knife to slice.