Heat oven to 350° F.
Spray three 8 inch x 4 inch loaf pans with baking spray. Set aside.
In a medium bowl, mash bananas and buttermilk together. Set aside.
In a large bowl, mix sugars, eggs, oil, and vanilla.
Add flour, salt, baking soda, baking powder, and cinnamon.
Mix only to combine.
Add bananas and stir until well combined.
Stir in cranberries and walnuts.
Divide batter evenly between prepared pans.
Top each loaf generously with streusel.
Bake for 40-45 minutes, or until done.