Preheat oven to 350 degrees. Wash beets, wrap in aluminum foil and bake until tip of knife easily pierces the beet, about 1 1/2 hours. Cool beets, peel and process in a food processor until finely chopped. Measure 1 cup of the puree and set aside.
Preheat oven to 350 degrees. Butter and flour two 9 inch round cake pans. In a medium bowl, combine the flour, cocoa powder, baking powder, salt and mix well. Pour cup of beet puree back in the food processor, add buttermilk, lemon juice, vinegar, vanilla and puree until smooth. In a large bowl, use an electric mixer and beat sugar and butter until well blended. Add eggs 1 at a time, beating well. Mix in dry ingredients in 3 equal amounts alternating with 2 additions of the buttermilk/beet mixture. Pour the batter evenly between the two prepared cake pans. Bake for approximately 25 minutes or until a toothpick comes out clean. Cool cake completely before frosting.
For frosting, beat cream cheese and butter in a large bowl until fully blended. Add vanilla, powdered sugar and mix until smooth and fully blended. Place 1 cake layer on a cake plate and spread 1 cup frosting over top. Place berries on top of frosting, pressing lightly to adhere. Place second cake layer on top and finish with the remaining frosting over top and sides of cake. Arrange remaining berries decoratively over top of cake and along bottom. Serves 8-10.
To achieve a true red color, skip beets, add 1 T of red food coloring and replace 1 tsp of baking powder with 1 tsp of baking soda.