Preheat your oven to 350°F. Line a muffin tin with paper liners or grease with non-stick cooking spray.
In a large mixing bowl, whisk together the flour, baking powder, baking soda, salt, and sugar until well combined.
In a separate bowl, mix together the melted butter, egg, vanilla extract, buttermilk, and mashed bananas until smooth.
Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix; a few lumps are okay.
Divide the batter evenly among the prepared muffin cups, filling each about ¾ full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for 5 minutes before transferring them to a wire rack to cool completely.
Serve and enjoy!
Notes
Stir the wet and dry ingredients together until just combined. Overmixing can make the muffins tough instead of light and fluffy.
The riper the bananas, the sweeter and more flavorful your muffins will be. Look for bananas with lots of brown spots on the peel.
If you don’t have buttermilk on hand, you can make a quick substitute by mixing ½ cup of milk with ½ tablespoon of lemon juice or vinegar. Let it sit for 5 minutes before using.
Start checking your muffins around the 18-minute mark. If a toothpick inserted into the center comes out clean, they’re done.