- 2 large beets, trimmed
- 1/2 cup sour cream
- 5 1/2 teaspoons Champagne vinegar or white wine vinegar
- 2 teaspoons prepared white horseradish
- 1 1/4 teaspoons sugar
- 2 bunches watercress, tough stems trimmed
- 2 tablespoons corn oil
- 16 1/3-inch-thick rounds unpeeled English hothouse cucumber
- Preheat oven to 400°F. Wrap beets in foil. Bake until tender when pierced with fork, about 1 hour 15 minutes. Cool. Peel beets. Cut each beet into 8 rounds. Whisk sour cream, 1 1/2 teaspoons vinegar, horseradish, and sugar in bowl to blend. Season dressing with salt and pepper. (Beets and dressing can be made 1 day ahead. Cover separately and chill.)
- Toss watercress with corn oil and remaining 4 teaspoons vinegar in large bowl. Season with salt and pepper. Divide watercress among 4 plates. Overlap beet slices and cucumber slices atop each. Drizzle with dressing and serve.