Preheat oven to 425°.
Leave root and 1 inch of stem on beets; scrub with a brush. Place beets on a baking sheet lined with foil; bake at 425° for 45 minutes or until tender. Cool slightly. Peel beets; cut each into 8 wedges.
Combine rind, greens, tangerine sections, and feta in a large bowl. Combine tangerine juice, pepper, lemon juice, oil, salt, and mustard; stir well with a whisk. Pour over salad mixture; toss to combine. Place salad mixture on each of 4 plates; top with beets.