Heat oven to 350F. Spray bundt pan with nonstick cooking spray.
In a mixing bowl whisk together the flour, baking powder, baking soda, and salt.
2 cup unbleached, all-purpose flour, 2 teaspoon baking powder, ¼ teaspoon baking soda, ¼ teaspoon salt
In another mixing bowl (I used my Kitchenaid), combine the oil, sugar, and bananas. Beat until smooth. Mix in the vanilla, eggs, and yogurt. Blend until smooth.
¾ cup neutral oil, 1 ¼ cup brown sugar, 3 ripe bananas, 2 teaspoon vanilla extract, 3 egg, 6 tablespoon plain yogurt
Fold wet ingredients in dry ingredients, combining just until blended.
Divide the batter into two bowls, about ⅗ in one and ⅖ in the other.
Add the cocoa powder to the smaller amount of batter and stir until just combined.
⅓ cup unsweetened cocoa powder
Spoon the two batters in dollops around the bundt pan, alternating the colors.
Use a knife to swirl the different colored batters together, taking care not to mix them too much.
Bake the for 35-40 minutes or until tester comes out with just a few crumbs attached. Cool the cake in the pan on a wire rack for 15 minutes. Carefully, run a rubber spatula around the edges of pan to loosen cake. Invert the pan onto a cooling rack and remove pan. Cool completely. Transfer to serving dish. Sift powdered sugar over top.
1 tablespoon powdered sugar
Notes
To freeze: Once the cake has cooled, wrap carefully in plastic wrap and place in a large ziptop bag. Remove as much air from the bag as possible and freeze. To serve, thaw completely. Sift over powdered sugar before serving.