Ingredients

• 1/2 cup well-shaken low-fat buttermilk
• 2 tablespoons low-fat sour cream
• 1 tablespoon mayonnaise
• 3/4 teaspoon finely chopped fresh tarragon or 1/4 teaspoon dried tarragon, crumbled
• 1/2 teaspoon minced garlic, mashed to a paste with 1/4 teaspoon salt
• 1/4 teaspoon dry mustard, or to taste
• 1/2 cup finely chopped red onion
• 1 small head red leaf lettuce (1/2 pound), torn into pieces
• 1 bunch watercress, coarse stems discarded
• 1 cup thinly sliced seedless cucumber (usually plastic-wrapped)

Instructions

1. Whisk together all dressing ingredients in a small bowl with salt and pepper to taste.
2. Make salad: Soak onion in 1 cup cold water 10 minutes, then drain well in a sieve. Toss lettuce, watercress, and cucumber together in a bowl and divide among 6 plates. Spoon dressing over, then sprinkle salads with onion.
3. Soak onion in 1 cup cold water 10 minutes, then drain well in a sieve.
4. Toss lettuce, watercress, and cucumber together in a bowl and divide among 6 plates. Spoon dressing over, then sprinkle salads with onion.