Preheat oven to 375 F. Line muffin tins with liners.
In a large bowl, combine flour, baking soda, baking powder, salt, cinnamon and nutmeg.
In a medium bowl, beat together the egg, bananas, white sugar, brown sugar, oil and vanilla extract. Stir into the flour mixture just until blended. Spoon batter into muffin cups.
In a small bowl, mix together brown sugar, flour and cinnamon. Cut in butter into mixture. Sprinkle topping over the muffins.
Bake for 18 minutes or until inserted toothpick comes out clean.
Recipe by Sugar, Spice and Family Life at https://sugarspiceandfamilylife.com/2014/04/banana-streusel-muffins.html