Preheat your oven to 350 degrees Fahrenheit. Spray a 9 by 5 inch bread pan well with cooking spray. In a large bowl, whisk together the flour, baking soda, and salt.
2 cups all purpose flour, 3/4 teaspoon baking soda, 1/2 teaspoon salt
In a medium bowl, whisk together the mashed bananas, cooled butter, eggs, sour cream, sugar, and vanilla.
3 very ripe bananas, 3/4 cup granulated sugar, 6 tablespoons unsalted butter, melted and cooled, 2 large eggs at room temperature and lightly whisked, 1/4 cup sour cream, 1 teaspoon vanilla extract
Gently fold the wet ingredients into the dry ingredients. Mix in the chopped walnuts.
1 cup walnuts
Pour the bread batter into the prepared pan. Bake for 55 minutes or until a toothpick inserted slightly off center in the bread comes out with just a few crumbs. If the bread isn't finished inside but is browning on the outside, you can tent it with foil and bake for 5 to 10 more minutes.
Allow the bread to cool in the pan for 10 minutes. Then remove and allow to cool on a wire rack for 1 hour before slicing and enjoying.