Preheat oven to 350 degrees.
Line muffin pan with baking cups or spray them lightly with cooking spray. Set aside.
In a large mixing bowl combine bananas, sugar and egg. Add melted butter and stir until combined.
In a separate bowl combine dry muffin ingredients. Add to wet ingredients and stir until just combined.
Using a 1/4 cup measuring cup divide up batter into prepared muffin pan. Set aside.
For the crumb topping, in a medium bowl, whisk together sugars and cinnamon. Pour the butter over top and using a wooden spoon, mix until incorporated. Then add the cake flour and mix until mixture resembles a thick and cohesive dough.
Sprinkle a generous amount of the crumb topping on top. Do not press the crumb topping into the batter. Let set on top of muffin batter.
Bake 20-25 minutes or until toothpick inserted comes out clean. If you wish for the crumb topping to have a darker brown appearance broil muffins for a few minutes, make sure to watch this closely.
Store muffins in air tight container for up to two days.