1/2 cup (1 stick) butter, at room temperature, plus more for pan
1 cup granulated sugar
2 large eggs
1 1/2 cups unbleached plain flour
1 teaspoon baking soda
1 teaspoon salt
1 cup mashed very ripe bananas (about 3)
1/2 cup sour cream (I used Fat Free Greek yogurt)
1 teaspoon vanilla
1/2 cup chopped walnuts or pecans (optional; I didn’t use them)
Preheat oven to 350 degrees. Butter a 9-by-5-by-3-inch loaf pan; set aside. In an electric mixer fitted with the paddle attachment, cream butter and sugar until light and fluffy. Add eggs, and beat to incorporate.
In a medium bowl, whisk together flour, baking soda, and salt. Add to the butter mixture, and mix until just combined. Add bananas, sour cream, and vanilla; mix to combine. Stir in nuts, and pour into prepared pan.