Preheat the oven to 350 degrees F. Lightly butter a non-stick bundt pan; coat with flour, shaking out excess. Set pan aside. In a bowl, whisk together flour, cocoa, baking soda, nutmeg and salt, and then set aside.
In another bowl, combine bananas and sour cream, and then set aside.
In large bowl beat the butter and sugar until light. Beat in the eggs. Beat in half the banana/sour cream mixture, and then beat in half the dry mixture. Repeat.
Pour into prepared pan. Bake 50-60 minutes, or until toothpick inserted in centre pulls out clean. Serve wedges of cake, if desired, with whipped cream or ice cream and slices of fresh banana.