Grandma's Banana Cake
From: Classic Home Desserts by Richard Sax

CAKE
2 1/4 cups cake flour (not self-rising), spooned lightly into measuring cups
1 1/2 teaspoons baking powder
1 1/2 teaspoons baking soda
1/4 teaspoon salt
3/4 cup (1 1/2 sticks) unsalted butter, softened
1 1/2 cups sugar
3 large eggs
2 teaspoons pure vanilla extract
3/4 generous cup very ripe mashed bananas (about 2)
1/4 cup plus 2 tablespoons sour cream or plain yogurt
Confectioner's sugar, for sprinkling (optional)

CHOCOLATE FROSTING (OPTIONAL)
1 1/2 cups sifted confectioners' sugar
3 ounces unsweetened chocolate, melted
2 tablespoons sour cream, or more as needed
2 tablespoons unsalted butter, softened
1/8 teaspoon salt
1 teaspoon pure vanilla extract

CAKE: Preheat the oven to 350 F. Generously butter a 10-inch tube or Bundt pan. Flour the pan, shaking out the excess; set aside. Sift the flour with the baking powder, baking soda and salt onto a sheet of wax paper; set aside.

Beat the butter with an electric mixer at medium-high speed until very light. Gradually beat in the sugar and continue to beat until fluffy. Beat in the eggs, one at a time; beat in the vanilla.

Lower the speed to very slow; add 1/2 of the flour mixture in batches, alternating with the mashed bananas. Add the remaining flour mixture in batches, alternating with the sour cream or yogurt. Don't overmix; finish folding the ingredients together by hand, with a few strokes of a large rubber spatula. Pour the batter into the prepared pan.

Bake until a toothpick inserted in the center of the cake emerges clean, 50 to 55 minutes. Do not overbake.

Cool the cake in the pan on a wire rack for 10 to 15 minutes. Run the tip of a knife around the cake to loosen it from the sides and tube of the pan, and carefully unmold. Cool to room temperature. Dust with confectioners' sugar or frost; serve in slices or wedges.

CHOCOLATE FROSTING (optional): With an electric mixer, combine the confectioners' sugar and melted chocolate at medium-slow speed. Increase the speed slightly, add the sour cream, butter, salt and vanilla and mix well until blended. If the frosting is too stiff, add more sour cream until the frosting is of a spreadable consistency.