Cream together the softened butter and 1 ½ cups sugar, just like you would when making cookie dough. Add in the eggs, mashed bananas, sour cream, and vanilla extract. Mix until thoroughly combined.
In a separate bowl, whisk together the all-purpose flour, 1 teaspoon cinnamon, salt, and baking soda.
Add the banana mixture to the dry ingredients and stir just until combined. Do not over mix.
Prepare two 9x5 loaf pans by spraying them with non-stick cooking spray.
Mix together ½ cup of sugar and 2 teaspoons of cinnamon and sprinkle over the cooking spray in each loaf pan.
Divide the batter between the pans.
Bake at 300 degrees for 1 hour or until a toothpick inserted comes out clean.
Allow the banana bread loaves to cool in the pan for 15 minutes before transferring to a cooling rack.