Preheat oven to 350 degrees. Add paper muffin liners to a 12-cup muffin tin.
In a large bowl, whisk together flour, baking powder, soda, salt, and cinnamon. Add wheat bran, coconut sugar, and walnuts, and whisk to combine.
In a medium bowl, mash 1 banana with a fork then add eggs, Greek yogurt, honey, and vanilla, stir to combine. Add coconut oil and stir until incorporated. Dice the second banana into small chunks and stir into mixture.
Pour liquid mixture into dry ingredients and stir just until dry ingredients are moist. Add batter to muffin liners. Batter should extend above the liners.
Bake muffins until a toothpick inserted in the center comes out clean, approximately 25 minutes.
Allow to cool completely before storing in an airtight container. These muffins are very moist and even better the second day.
Tip: Do not refrigerate as this tends to dry them out. Feel free to freeze muffins after completely cooling.