Preheat the oven to 350°F and line a muffin tin with 6 liners. Only baking 6 at a time will allow for a better rise. Set aside.
In a saucepan over low heat, melt the butter. Allow to cool completely while you measure out the rest of the ingredients.
In a small bowl, add the flour, baking soda, baking powder, salt, and cinnamon. Whisk together.
In a large bowl, mash the ripe bananas with a fork or potato masher. Mash the bananas well. There will be some chunks that are unavoidable. Set aside.
In a large bowl, whisk together eggs, melted butter, vanilla, white sugar, and brown sugar.
Add the mashed bananas and gently whisk for a few seconds until incorporated. Do not overmix.
Add the dry ingredients into the wet ingredients. Using a spatula, fold until no flour streaks appear and a batter has formed.
Use a cookie scoop to scoop 1 scoop of batter into the 6 muffins liners. Spoon 1/2 tsp of Nutella on top. Use a toothpick or knife to lightly swirl it together. Add another scoop of batter on top, the muffin liner will be full. Add another 1/2 tsp of Nutella and swirl it on top.
Bake for 20-22 minutes or until a toothpick comes out the center clean.
Allow the muffins to sit in the hot pan for 10 minutes. Serve warm and enjoy!