Preheat your oven to 350°F (175°C).

Line your muffin tin with paper liners or grease it with unsalted butter.

In a medium bowl, combine all-purpose flour, baking powder, ground cinnamon, and salt.

In a large bowl, mash the ripe bananas and mix in the brown sugar, eggs, and melted butter.

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

In a small bowl, mix together flour, brown sugar, and ground cinnamon for the streusel topping, then cut in the cold butter.

Spoon the muffin batter into each prepared muffin cup, and sprinkle the streusel topping over each muffin.

Bake for 18-20 minutes until golden brown and a toothpick comes out clean.

Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack.