preheat the oven to 375 degrees. Lightly spray a 12 count muffin pan with nonstick cooking spray or line with cupcake liners.
In a large bowl, beat the mashed bananas and brown sugar together. Add in the vegetable oil, egg and lemon juice and again mix well.
In a separate bowl, mix the flour, baking soda, baking powder and salt. Add the dry ingredient to the wet ingredients and combine.
In a third bowl, add the ingredients for the crumb topping. Use a fork to cut the butter in and then use your fingers until the mixture resembles coarse sand.
Scoop the muffin batter into the prepared pan filling each about 2/3 full.
Sprinkle the crumb topping on top of each muffin until fully covered.
Bake the muffins for 18-20 minutes or until the tops are golden brown and a toothpick inserted in the middle comes out clean.
Remove the muffins from the oven and remove them from the muffin tin. Cool the muffins on a wire rack.
Store in an airtight container.