01 - Preheat oven to 350°F. Grease and flour a 9x5-inch loaf pan, or line with parchment paper.
02 - In a large mixing bowl, whisk together mashed bananas, melted butter, eggs, yogurt or sour cream, and vanilla extract until smooth.
03 - In a separate bowl, stir together flour, granulated sugar, brown sugar, baking soda, baking powder, salt, and cinnamon.
04 - Gently fold dry ingredients into wet mixture, mixing just until combined. Do not overmix.
05 - Fold in nuts or chocolate chips if using.
06 - Pour batter into prepared loaf pan and smooth top with spatula.
07 - Bake for 50-60 minutes, or until toothpick inserted into center comes out clean or with just a few moist crumbs.
08 - Cool in pan for 10 minutes, then turn out onto wire rack to cool completely before slicing.