From Vegetable Love, by Barbara Kafka (Artisan Books)
3 small beets, boiled until tender, skins removed, and quartered
1/4 cup buttermilk
2 cups all-purpose flour
1 teaspoon kosher salt
1/2 teaspoon baking soda
8 tablespoons cold unsalted butter, cut into small cubes
Place a rack in the center of the oven, heat to 500 degrees F. In a food processor, puree the cooked beets; there should be 1 cup beet puree. Transfer to a bowl. Whisk in the buttermilk. Sift the dry ingredients into a medium mixing bowl. Cut in the butter until the largest pieces are the size of small peas. Place in the freezer or refrigerator until the butter is hard, 10 to 15 minutes.
Scrape the beet puree into the flour mixture and stir with a wooden spoon just until the dough comes together around the spoon. This will be a very moist, sticky dough; there should still be whole pieces of butter visible in the dough. Turn dough out onto a well-floured surface. Knead about 10 times, incorporating enough flour so the dough no longer sticks to hands. Keep the board well-floured. Pat the dough out 1/2-inch thick. Using a biscuit cutter or a glass, cut into 16 two-inch rounds. Place on an ungreased air-cushioned cookie sheet or heavy baking sheet, preferably black. Bake 9 to 11 minutes, or until cooked through. Allow to cool for a few minutes before serving.