Preheat the oven to 350 degrees F and line a muffin pan with muffin papers.

In a small bowl, stir together the ground flax seed and water. Allow mixture to sit at least 10 minutes, until it reaches the consistency of beaten eggs. Stir mixture occasionally as it sits.

In a mixing bowl, mash the bananas and whisk in the flax eggs and pure vanilla extract. Stir until well combined (it's okay if the banana stays chunky).

In a separate bowl, stir together the remaining ingredients. Pour the dry ingredients into the bowl with the wet and stir well until combined.

Fill the muffin holes with the banana muffin batter. Bake on the center rack of the preheated oven for 28 to 35 minutes, until muffins are cooked through and lightly golden-brown around the edges.

Allow muffins to sit at least 30 minutes before peeling off the muffin papers and eating.