Step 1Trim greens from beets, leaving 1 inch of stems, and steam beets until tender, 15 to 25 minutes, depending on their size. Peel, quarter and set aside.
Step 2Discard stems and any greens that don't look up to snuff. Steam greens until tender, about 5 minutes, then toss with half the butter and season with salt and pepper. Arrange them in a nest on a plate.
Step 3In another skillet, heat beets with remaining butter over medium heat. Add vinegar and shake pan until it evaporates, 30 seconds. Spoon beets into center of greens and serve.