Heat oven to 400 F. Cut greens off of beets. Rinse greens under cold running water, drain well and reserve.
Wash beets. Drizzle a bit of olive oil onto your hands and rub beets to coat them lightly. Wrap beets in foil and bake for about 45 minutes or until tender. Cool until you can handle and then pull off the outer skin. Slice and set aside.
Cut beet greens into strips and place in mixing bowl. Chop celery, cabbage and onion, and add to bowl. Zest and juice 1 orange into bowl. Peel the other orange and cut into segments. Add to bowl. Drizzle 1/2 tablespoon olive oil over the salad. Season with black pepper and toss to combine.
Arrange salad on chilled plates and top with sliced beets. Serve immediately.