Preheat oven to 350°F (175°C). Grease or line a 9×5-inch loaf pan with parchment paper.

In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.

In a large bowl, mash the ripe bananas with a fork until mostly smooth but still with some texture.

Add the melted butter, brown sugar, eggs, sour cream, and vanilla extract to the mashed bananas. Whisk until well combined.

Add the dry ingredients to the wet ingredients. Using a rubber spatula, gently fold together until just combined with a few streaks of flour still visible.

If using, fold in optional mix-ins like nuts or chocolate chips with minimal stirring.

Pour the batter into the prepared loaf pan and smooth the top with a spatula.

Bake in the preheated oven for 55-65 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Allow to cool in the pan for 10 minutes, then remove to a wire rack to cool completely for at least 1 hour before slicing.

Store wrapped tightly at room temperature for up to 4 days or freeze for up to 3 months.