1 cup unsweetened cocoa powder (not Dutch-process)
1 teaspoon baking soda
3/4 teaspoon salt
2 very ripe bananas, mashed
1/2 cup sour cream
1 stick (1/2 cup) unsalted butter, softened
1 cup granulated sugar
1/2 cup firmly packed light brown sugar
2 extra-large eggs
1 tablespoon coffee extract, or 1 tablespoon instant espresso powder dissolved in 1 tablespoon hot water
1 teaspoon vanilla extract
Garnish: confectioners' sugar
Directions
Preheat oven to 350°F. and grease and flour a 10-inch (3-quart) bundt pan, knocking out excess flour.
Into a large bowl sift together flour, cocoa powder, baking soda, and salt. In a small bowl stir together bananas and sour cream. In another large bowl with an electric mixer beat together butter and sugars until light and fluffy and add eggs, 1 at a time, beating well after each addition. Beat in coffee extract (or espresso) and vanilla. Beat in flour mixture in batches alternately with banana mixture, beginning and ending with flour mixture, until batter is just combined.
Spoon batter into pan and bake in middle of oven 50 minutes, or until a cake tester comes out clean and cake pulls away from side of pan. Cool cake in pan 10 minutes and invert onto a rack to cool completely. Let cake stand, wrapped tightly, at room temperature overnight.
