Preheat your oven to 350°F (175°C). Line a 12-cup muffin pan with paper liners. This keeps the muffins from sticking and makes serving and cleanup much easier later.

In a medium bowl, combine the flour, baking soda, baking powder, salt, and cinnamon. Whisk everything together until evenly mixed. This step helps distribute the leavening ingredients throughout the batter.

Place the ripe bananas into a large mixing bowl. Mash them with a fork until mostly smooth. A few small lumps are fine because they add extra texture and flavor.

Add the brown sugar, melted butter, eggs, vanilla extract, and milk to the mashed bananas. Whisk until the mixture becomes smooth and creamy. Make sure everything is well combined before moving on.

Gradually add the dry ingredients to the wet ingredients. Stir gently with a rubber spatula until no dry flour remains. Be careful not to overmix or the muffins may become dense.

Using a spoon or ice cream scoop, divide the batter evenly among the muffin cups. Fill each cup about three-quarters full so the muffins have room to rise beautifully.

Mix the brown sugar and cinnamon in a small bowl. Sprinkle the mixture evenly over each muffin. This simple topping creates a sweet and slightly crisp bakery-style finish.

Place the muffin pan in the preheated oven. Bake for 18 to 20 minutes. The muffins are done when a toothpick inserted into the center comes out clean.

Remove the muffins from the oven and let them cool in the pan for five minutes. Transfer them to a wire rack and allow them to cool completely before serving.