Preheat the oven to 350°F or 180ºC with an oven rack in the bottom third of the oven.
Mash the bananas with a fork and set aside.
Add the mashed bananas, coconut milk and flax egg to the bowl and mix again.
Finally, add the vanilla seeds and chopped walnuts and stir until all the ingredients are well combined.
Line a 9×5-inch (23×13 cm) loaf pan with parchment paper or grease it with some coconut oil. Add the batter to the pan and bake for 60 to 75 minutes (our banana bread was ready in 70 minutes). Stick a toothpick into the center of the loaf and if it comes out clean, the loaf is done. Cover the top with foil if the banana bread gets browned, but the middle isn’t done.
Let cool completely before cutting.
Keep the banana bread in a sealed container at room temperature for several days.