Preheat oven to 350°F. Spray two 9 in. cake pans with vegetable pan spray.
In large bowl, beat together pureed beets and eggs with electric mixer until well mixed. Add oil, buttermilk, melted chocolate and vanilla. Beat until well combined. In separate bowl, combine flour, sugar, cocoa powder, salt, baking soda and baking powder. Add dry ingredients to wet ingredients; mix until well combined. Divide batter equally between prepared pans.
Bake 36-40 minutes or until toothpick in center comes out clean and top of cake springs back when lightly touched. Cool cake in pan 10 minutes; turn out to a cooling rack. Cool completely.
Makes about 7 cups batter.