Mix the dry ingredients together by adding the salt, baking powder, baking soda, and cinnamon to the flour.
In a separate bowl, smash the ripe bananas, add the egg, sugar, vanilla extract, and the melted butter, and combine everything using a wooden spoon or a spatula.
Add the dry ingredients to the wet ones and mix together.
Line a muffin baking tray with paper liners and divide the batter into 12.
Crunchy Topping
Mix all the ingredients together until you have wet sand-like texture.
Divide the crumb on top of the muffins.
Bake the muffins in an oven preheated to 175C (347C) for 18 to 20 minutes, until the top is golden brown.
Wait for the muffins to be totally cool before storing them in a closed food box for the topping to stay crunchy.