The absolute BEST banana crumb muffins with a delicious crumb topping!
Preheat oven to 375 degrees F. Lightly grease and flour 10 cavities in a muffin tin. Fill the other two muffin cavities halfway with water (ensures even baking)
In a large bowl, mix together the flour, baking soda, baking powder, salt, cinnamon, and nutmeg. In another bowl, beat together bananas, white sugar, brown sugar, egg, melted butter, and vanilla extract. Stir the banana mixture into the flour mixture until JUST combined. Do not overmix (will result in denser muffins). Spoon batter into prepared muffin cups.
In a small bowl, make the crumb topping: combine the brown sugar, white sugar, flour, and cinnamon. Whisk until combined and then add in the melted butter and stir until crumbs form. Sprinkle this mixture evenly onto the 10 muffins.
Remove and allow to cool on a cooling rack. Muffins are best within 3 days.