1 cup sugar
½ cup unsalted butter, room temperature
2 large eggs, room temperature
1 teaspoon vanilla extract
3 large, overripe bananas, mashed
2 1/4 cups all-purpose flour
½ teaspoon baking powder
1 teaspoon baking soda
1 teaspoon ground cinnamon
1/4 teaspoon ground nutmeg
1/4 teaspoon ground allspice
3/4 cups sour cream, at room temperature
1 cup toasted walnuts, chopped
Preheat the oven to 350°F with the rack on the middle shelf. Grease and flour a 9H5 inch loaf pan (or coat with baking spray).
Combine the sugar and the butter in the bowl of a mixer fitted with the paddle attachment. Beat on medium-high until light and fluffy. Add in the eggs one at a time, beating until the first is fully incorporated before adding the second. Stir in the vanilla and the bananas.
In a separate bowl, whisk or sift together the flour, baking powder, baking soda, cinnamon, nutmeg, and allspice. Add the dry ingredients to the wet in three parts, mixing each addition until just combined. Stir in the sour cream (and the walnuts if using).
Pour the batter into the loaf pan. Bake until an inserted toothpick comes out with only a few crumbs attached (a perfectly clean toothpick indicates a slightly overdone loaf), approximately 50 minutes to 1 hour. If the loaf begins to become dark too quickly, tent with aluminum foil for the final 10-20 minutes.
Remove the loaf
from the oven and cool for 10 minutes. Turn out onto a wire rack and cool.
Slice and serve with salted butter or sour cream. To store, wrap in plastic
and keep at room temperature. If storing for longer than 2-3 days, wrap
tightly and freeze.