Step 1: Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan or line it with parchment paper for easy removal.
Step 2: In a large mixing bowl, cream together the softened butter and granulated sugar until the mixture is light and fluffy.
Step 3: Beat in the eggs one at a time, then stir in the vanilla extract, mashed bananas, and buttermilk until well combined.
Step 4: In a separate medium bowl, whisk together the flour, baking soda, salt, and cinnamon.
Step 5: Gradually add the dry ingredients to the wet ingredients, stirring gently just until combined; do not overmix.
Step 6: Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Step 7: Bake for 60 to 65 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs.
Step 8: Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.