In a large bowl of a mixer, fitted with a paddle attachment, 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.
Make the crumb topping by combining the powdered sugar, flour, cinnamon salt and melted butter. Using your hands, crumble the mixture over the batter in the pan. Bake in a pre-heated 350 degree oven for 45 – 50 minutes or until a toothpick comes out clean.