Chocolate Beet Cake, with beets in the frosting AND the cake.
2-3 beets, unpeeled but trimmed of their greens
1 teaspoon vegetable oil
6 ounces (3/4 cup) unsalted butter, softened, plus more for greasing the pans
1 cup packed brown sugar
3/4 cup granulated sugar
2 large eggs
1 teaspoon pure vanilla extract
2 cups all-purpose flour, plus more for dusting the pans
2/3 cup unsweetened natural cocoa powder
1 teaspoon baking soda
1/2 teaspoon baking powder
1 teaspoon salt
1 1/4 cup buttermilk
Frosting: 1 cup (2 sticks) unsalted butter (softened), 8 ounces (1 brick) cream cheese (softened), 4-5 cups powdered sugar (sifted), 2 tablespoons grated beets, 1 teaspoon pure vanilla extract or scrapings of one vanilla bean pod, 1-2 teaspoons milk (depending on desired consistency), 1-2 teaspoons fresh lemon juice, pinch of salt
Let's get Cooking...
Preheat oven to 375F.
Place beets on a piece of foil. Drizzle with just a it of oil then seal foil up. Place on a baking sheet in the oven. Roast until beets are tender when pierced with a knife, about 1 hour.
Remove the beets from the oven. Open the foil and allow beets to cool completely. Beets will be easy to peel (just using a paring knife) once completely cooled.
Grate the peeled beets on the finest grating plane. Measure 3/4 cups of grated beets for the cake and 2 tablespoons for the frosting. Set aside.
Reduce the oven temperature to 350F. Use butter to grease whatever you'll be baking the cake in. Set aside while you prepare the cake.
With an electric mixer, cream together butter and sugars. Beat on a medium speed until pale and fluffy, about 3-5 minutes. Beat in eggs, one at a time, for one minute after each addition. Stop the mixer and scrape down the sides of the bowl as necessary. Once eggs are incorporated, beat in the beets and vanilla extract until thoroughly combined.
In a medium bowl, whisk together flour, cocoa powder, baking soda, baking powder, and salt.
Add half of the dry ingredients to the butter and egg mixture. Beating on low speed, slowly add the buttermilk. Once just incorporated, add the other half of the dry ingredients. Beat on medium speed until milk and dry ingredients are just incorporated. Try not to overmix the batter.
Pour the batter into the cake pan. Joy suggests dividing the batter between two cake pans, which then bake for 23-25 minutes (for a 9-inch pan) or 30-32 minutes (for an 8-inch pan). But I'm not that fancy.
Cake is done when a skewer inserted in the center comes out clean. Remove from the oven and allow to rest for 10 minutes. Invert cakes onto a cooling rack to cool completely before frosting and assembling the cake.
To make the frosting: Beat cream cheese for 30 seconds, until pliable and smooth. Add the butter and beat for another 30 seconds, until well combined. Stop the mixer and scrape down the bowl as necessary. Beat in the beets. Add the powdered sugar, vanilla extract, milk, lemon juice, and salt. Beat on medium speed until smooth and silky. Refrigerate the frosting for 30 minutes before frosting the cooled cakes.
** Cake will last, well wrapped in the refrigerator, for up to 4 days.