Preheat the oven to 350 degrees. Coat a muffin tray with cooking spray.
In a large bowl, mix the flour, baking powder, salt, baking soda, white sugar, and brown sugar until well combined.
Preheat the oven to 425 degrees. Coat a muffin tray with cooking spray.
Mix the flour, baking powder, baking soda, and salt until well combined.
In another bowl, mix the oil, yogurt, white sugar, brown sugar, egg, vanilla, and mashed bananas until mixed thoroughly.
Slowly combine the dry ingredients into the wet ingredients without overmixing.
Add the coconut and walnuts, then fold them into the batter.
Pour the batter evenly into the prepared muffin tray.
Bake the muffins at 425 degrees for 5 minutes, then, without opening the oven door, reduce the oven temperature to 350 degrees and bake for an additional 13-15 minutes, or until a toothpick inserted in the center comes out clean. Side Note: This helps create a dome on top of the muffin.
Allow the muffins to cool for 5 minutes in the muffin tray, then transfer to a wire rack to continue cooling.