Preheat oven to 350 degrees.
Grease two 8x5 inch loaf pans and line with a parchment paper sling. Grease the parchment paper too.
In a large mixing bowl mash the bananas. Add the oil, eggs, sugar and lemon juice to the bowl and whisk to combine.
In another bowl, add the flour, baking powder, baking soda, and salt. Whisk to combine.
Gradually fold the dry ingredients into the wet ingredients until combined.
Fold in chopped nuts.
Divide the batter between the two prepared pans.
For the crumb topping: in a bowl add softened butter, brown sugar and flour. Mix with a fork until crumbly.
Top the banana breads evenly.
Bake for 45 minutes.
Let cool 15 minutes on a wire rack then take the banana breads out of the plans and completely cool on a wire rack.