Preheat your oven to 350°F (175°C) and grease a standard loaf pan with butter or cooking spray.

Mash 2-3 ripe bananas in a large mixing bowl until smooth and creamy.

Combine granulated sugar, brown sugar, melted butter, and a beaten egg into the bowl with the mashed bananas and mix until fully incorporated.

In a separate bowl, whisk together all-purpose flour, baking soda, and ground cinnamon, then add to the wet mixture and stir until just combined.

For the crumb topping, mix brown sugar, all-purpose flour, ground cinnamon, and melted butter in a small bowl until it forms coarse crumbs.

Pour the batter into the prepared loaf pan and sprinkle the crumb topping over the surface, pressing it down lightly.

Bake for 60-65 minutes; check for doneness with a toothpick.

Let the loaf cool for 10 minutes on a wire rack, then turn it out and allow to cool completely before slicing.