Cinnamon Crumb Banana Bread

I made this for the girls I visit teach and they all text me asking for the recipe, it was delicious!
(from littlebitsof.com)

Ingredients 

1 egg
1 cup sugar
1/2 cup unsalted butter, at room temp (I used coconut oil)
1 teaspoon vanilla
1/2 cup buttermilk
2 overripe bananas, mashed
2 cup all purpose flour
1/2 teaspoon salt
1/2 teaspoon baking soda
1 teaspoon baking powder
1 teaspoon cinnamon

Crumb Topping 

1/2 cup powdered sugar
1/2 cup all purpose flour
4 tablespoons unsalted butter, melted
1/2 teaspoon cinnamon
pinch of salt

In a large bowl of a mixer, beat together the sugar, egg and vanilla until combined. Add the butter and beat until smooth and the butter is fully incorporated. Beat in the buttermilk and bananas.

In a separate bowl, mix together the flour, salt, baking soda, baking powder, and cinnamon. Slowly stir the dry ingredients into the wet until all the flour is incorporated. Spray a loaf pan with non-stick spray and pour in the batter. *Note that not all loaf pans are the same size. You may have extra batter, so just pour in enough so there is still about an inch or 2 of space before the top of the pan. (I doubled the recipe and got 3 loafs).

Make the crumb topping by combining the powdered sugar, flour, cinnamon, salt, melted butter. Using your hands, crumble the mixture over the batter in the pan. Bake in the pre-heated 350 degree oven for 45-50 minutes or until a toothpick comes out clean.