Cut green tops off beets; discard. Wash beets; do not peel.
In a small saucepan bring a small amount of lightly salted water to boiling. Add beets. Cook, covered, over medium heat for about 20 minutes or until crisp-tender. Drain. Allow beets to stand until cool enough to handle (about 10 minutes). Under a running faucet, slip skins off beets.
In a serving bowl toss beets with olive oil, vinegar, and salt. Sprinkle with watercress and tarragon. Makes 4 servings.