Preheat the oven to 350 degrees. Lightly grease the bottom of a 9×13 baking pan. Sift the three flours together. Add cocoa, xanthan gum, baking powder, and baking soda to the flours and whisk together in a med. bowl. Beat the butter until creamy . Slowly add the brown sugar and the granulated sugar; whip until fluffy. Add the eggs and the egg yolks one at a time. Add the vanilla. Turn the mixer to low and alternately add the flour mixture and the buttermilk. Pour into the prepared pan. Bake for 30-35 minutes until the cake is springy to the touch.
Since this was truly a no-frills chocolate cake, I made a simple frosting. Feel free to substitute your favorite frosting. This one is not very sweet, but my toddler loved it.
5 oz. semi-sweet chocolate.
1/2 cup sour cream.
1/2 teaspoon vanilla.
1-2 Tablespoons whipping cream.
Directions: Melt chocolate in the microwave or over a double boiler. Let the chocolate cool until warm. Stir in the sour cream and vanilla. Add whipping cream to desired consistency. The frosting will thicken slightly as it cools. Once the cake has cooled, frost the cake. This frosting provided a simple, thin layer of frosting for my no-frills chocolate cake.