The Best Banana Bread

Name: The Best Banana Bread
Ingredients: ½ cup (1 stick) butter, at room temperature, plus more for pan; 1 cup sugar; 2 large eggs; 1 ½ cups unbleached all-purpose flour; 1 teaspoon baking soda; 1 teaspoon kosher salt; 1 cup mashed very ripe bananas; ½ cup sour cream; 1 teaspoon pure vanilla extract; ½ cup chopped walnuts or pecans