Preheat the oven to 375℉. Line a 12 cup muffin pan with paper liners.
In a large bowl, whisk together the flour, baking soda, baking powder, cinnamon, nutmeg and salt. Set aside. In a separate bowl, whisk together the bananas, sugars, egg, butter and vanilla. Whisk in the dry ingredients. Spoon into the prepared muffin cups.
Prepare the crumb topping: In a small bowl, use a fork to mix the sugar, flour, butter and cinnamon. Sprinkle the crumb topping over the batter in each cup.
Bake 18 to 20 minutes, or until the muffins are cooked through in the center (use a toothpick to test coming out clean).