Preheat your oven to 350°F (175°C). Prepare your muffin tin by lining it with muffin liners or greasing it with non-stick spray.
In a large mixing bowl, whisk together the 1 cup of all-purpose flour, baking soda, baking powder, salt, and 1 teaspoon of ground cinnamon.
In another bowl, mash the 3 ripe bananas with a fork until smooth. Add in the granulated sugar, brown sugar, egg, vegetable oil, and vanilla extract. Mix until well combined.
Pour the wet ingredients into the dry ingredients. Using a rubber spatula, gently fold the mixture together until just combined.
In a small bowl, combine 2 tablespoons of all-purpose flour, ½ teaspoon of ground cinnamon, and the cold butter. Mix until crumbly.
Divide the muffin batter evenly among the muffin cups, filling each about two-thirds full. Sprinkle the crumb topping generously over each muffin.
Place the muffin tin in the preheated oven and bake for 18-22 minutes, or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the tin for about 5 minutes before transferring them to a wire rack. Enjoy your warm Banana Crumb Muffins fresh out of the oven!
