Preheat the Oven & Prepare the Muffin Tin
Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or lightly grease it with butter or cooking spray.
Mix the Dry Ingredients
In a medium bowl, whisk together the flour, baking soda, baking powder, salt, and cinnamon (if using). Set aside.
Mash the Bananas
In a large bowl, mash the ripe bananas with a fork until mostly smooth. A few small lumps are okay!
Add Wet Ingredients
Stir in the sugar, egg, vegetable oil (or melted butter), and vanilla extract until everything is well combined.
Combine Wet and Dry Mixtures
Slowly add the dry ingredients into the wet mixture, stirring gently. Be careful not to overmix—stop once there are no large streaks of flour. If you’re adding chocolate chips or nuts, gently fold them in now.
Fill the Muffin Cups
Spoon the batter evenly into the muffin tin, filling each cup about ¾ full.
Bake
Place in the preheated oven and bake for 18–22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Cool & Enjoy!
Let the muffins cool in the tin for about 5 minutes, then transfer them to a cooling rack. Enjoy warm or at room temperature!