Preheat your oven to 350°F (175°C) and prepare your baking pan by greasing or lining it with parchment paper.

Mash the ripe bananas in a large mixing bowl until smooth, then add melted butter, brown sugar, eggs, and vanilla extract, mixing until combined.

In a separate bowl, whisk together flour, baking soda, salt, and cinnamon, then gently combine with the banana mixture until just moistened.

Prepare the streusel by mixing brown sugar, flour, cold butter, cinnamon, and a pinch of salt until crumbly, then set aside.

Pour the banana batter into the loaf pan and sprinkle the streusel topping generously over the top.

Bake in the oven for 55–65 minutes until golden brown, checking with a toothpick for doneness.

Once baked, cool the banana bread in the pan for 10 minutes, then transfer it to a wire rack to cool completely before slicing.