Preheat oven to 350 degree.
Coat muffin pans with non-stick spray, or use paper liners.
Sift together the flour, baking powder, baking soda, and salt,set aside.
Combine bananas, sugar, egg, vanilla and melted butter in a large bowl.
Fold in flour mixture, blueberries and mix until dry ingredients are just combined. Do not over mix.
Fill the muffin cups till 3/4th mark.
Bake in preheated oven for 15-20 minutes.
These stays well upto 3 days if stored in air tight container.