Preheat the oven to 350°F (175°C). Grease a loaf pan.

In a mixing bowl, combine the mashed bananas, granulated sugar, brown sugar, melted butter, eggs, and vanilla extract. Mix well.

In another bowl, whisk together the flour, baking soda, salt, and cinnamon.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

In a small bowl, mix the topping ingredients: brown sugar, cinnamon, and walnuts.

Pour half of the banana bread batter into the prepared loaf pan. Sprinkle half of the topping mixture over the batter.

Add the remaining batter and top with the rest of the topping mixture.

Bake in the preheated oven for 45-50 minutes, or until a toothpick inserted into the center comes out clean.

Allow to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.