Heat oven to 350 degrees.
In a large mixing bowl cream together the butter and sugar. Set aside.
Add in eggs, bananas, and vanilla. Mix until combined.
In a separate bowl mix the flour, baking soda, salt, and cinnamon.
Add the flour mixture along with the buttermilk to the brown sugar mixture and stir until blended. Do not over mix.
Place half of the batter into the 2 pans. So each pan has about the same amount.
In another small bowl combine the cinnamon and sugar.
Sprinkle the loaf pans with the cinnamon and sugar mixture. Swirl the mixture in with a knife.
The place the other half of the batter over the top of the cinnamon/sugar mixture.
Prepare the streusel topping by mixing the ingredients together.
Sprinkle the crumble topping over the batter.
Bake for about 43-45 minutes or until done in middle.