Preparation Preheat oven to 400°F. Wrap beets tightly in foil. Bake until tender, about 1 hour. Cool; peel beets. Coarsely shred beets. Whisk sour cream, onion, vinegar, sugar and mustard in small bowl to blend. Season with salt and pepper. Place lettuces in large bowl. Add dressing and toss to coat. Divide salad among 4 plates. Top each with beets, dividing equally.
Preparation Preheat oven to 400°F. Wrap beets tightly in foil. Bake until tender, about 1 hour. Cool; peel beets. Coarsely shred beets. Whisk sour cream, onion, vinegar, sugar and mustard in small bowl to blend. Season with salt and pepper. Place lettuces in large bowl. Add dressing and toss to coat. Divide salad among 4 plates. Top each with beets, dividing equally.