Tangy horseradish and dill dress pickled beets in this simple, colorful side dish. Make it a meal: Serve alongside Smorgastarta.
Drain pickled beets, reserving 1/4 cup of the juice. Toss onions with the reserved pickled beet juice in a medium bowl and let stand for 10 minutes.
Meanwhile, cut beet slices in half. Add to the onions along with horseradish, sour cream and dill (or parsley). Toss to combine. Season with salt and pepper.