Preheat the oven to 375°F (190°C) and line a muffin tin with paper liners.
In a large mixing bowl, mash the ripe bananas until smooth.
Add the egg, granulated sugar, melted butter, and vanilla extract to the bowl with the mashed bananas. Mix well to combine.
In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, ground cinnamon, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
Gently fold in the fresh blueberries.
Divide the batter evenly among the prepared muffin cups.
Sprinkle the tops with brown sugar or turbinado if desired.
Bake in the preheated oven for about 20-25 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for a few minutes before transferring to a wire rack to cool completely.
Serve and enjoy!
