Boil the whole, unpeeled beets in water to just cover until tender. Drain and cool. Slice the onions into thin crescents. Blanch onions for 1 minute and drain. Place onions in a mixing bowl. Combine vinegars and oil. Pour over the onions. Set aside to marinate. Peel and slice the beets. Add the beets to the bowl with onions. Toss gently and marinate for 30 minutes. Remove drain and serve over a bed of salad greens.
Per serving - 219 calories, 19 g fat (75% calories from fat), 2 g protein, 12 g carbohydrate, 4 g fiber, 0 mg cholesterol, 369 mg sodium