Preheat the Oven: Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan.
Mash the Bananas: In a large bowl, mash the ripe bananas until smooth.
Mix Wet Ingredients: Add eggs, granulated sugar, brown sugar, vegetable oil, vanilla extract, and buttermilk. Whisk until well combined.
Combine Dry Ingredients: In another bowl, sift together flour, baking soda, salt, and cinnamon.
Mix Everything Together: Gradually add the dry ingredients to the wet ingredients, stirring gently. Be careful not to overmix. Fold in walnuts (optional).
Pour into the Pan: Pour the batter into the greased loaf pan and smooth the top with a spatula.
Bake: Bake in the preheated oven for 55-65 minutes, or until a toothpick inserted into the center comes out clean.
Cool and Serve: Let the banana bread cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely before slicing.