Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan.

In a mixing bowl, mash the ripe bananas until smooth.

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

In another bowl, whisk together the flour, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.

If using, fold in the chopped walnuts.

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

Bake in the preheated oven for 55-60 minutes, or until a toothpick inserted into the center comes out clean.

Allow the bread to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.