Preheat oven to 350 degrees. Spray a 9 x 5 inch loaf pan with cooking spray.

In a small bowl, mix together the 3 Tbsp flour, 3 Tbsp sugar, and 1/2 tsp cinnamon for the streusel topping. Add the 3 Tbsp butter and cut in until crumbly with pea sized pieces. Set aside.

In a large mixing bowl, beat together the banana, melted and cooled butter, sugar, egg, milk, and vanilla. Add the flour, baking powder, salt, and cinnamon. Fold the mixture together just until combined.

Spread batter into the prepared loaf pan. Sprinkle streusel evenly over the top of the batter.

Bake at 350 degrees for 1 hour or until toothpick inserted in the center comes out clean. Let sit for 5 minutes and remove from pan and place on a cooling rack. Allow to cool for at least 15 minutes before serving. Makes 1 loaf.