Beet greens taste a lot like chard; you can treat them exactly the same way in the kitchen. Steaming or blanching quickly, then sautéing in olive oil with garlic and red pepper flakes or in bacon fat, are popular preps. The stems take longer to cook than the leaves, so chop them up and let them cook for a few minutes before you add the leaves. Or save them to add to a vegetable soup, suggests violabratsche. Many like to combine beet greens with the beets they came with for a dish of striking color and flavor contrasts. Some even recommend salads of raw, tender beet greens and roasted or steamed beets dressed with a vinaigrette.
Board Link: Ideas for Beet Greens, Please?