Using mandolin on thinnest setting, thinly slice beets.
Heat large nonstick skillet over medium heat; cook bacon for 4 to 5 minutes or until crisp. Remove with slatted spoon and set aside. Add prunes to skillet; cook for about 2 minutes or until heated through. Remove and reserve drippings.
Divide beets evenly among 4 plates. Sprinkle mache over beets; crumble Feta over top.
Top salads with bacon, prunes and reserved drippings. Drizzle with lemon juice. Sprinkle with pepper. Serve immediately.