Seafood Salad with Creamy Tarragon Dressing

• 1 pound peeled, deveined medium shrimp
• 1/2 pound bay scallops
• 1/2 pound cleaned calamari, cut into 1/2-in.-wide rings
• 1/2 cup mayonnaise
• 1 teaspoon grated lemon peel
• 1/4 cup fresh lemon juice
• 1/4 cup coarsely chopped fresh tarragon
• 1 tablespoon Dijon mustard
• About 1/2 tsp. kosher salt
• About 1/2 tsp. pepper
• 1/2 cup coarsely chopped watercress leaves
• 1/4 cup drained capers
• 1 avocado, pitted, peeled, and diced

Bring a large pot of water to a boil over high heat. Add shrimp, scallops, and calamari. Cover, remove from heat, and let steep just until shrimp are pink on the outside and opaque but still moist-looking in center of thickest part (cut to test), about 3 minutes. Drain seafood and immerse in ice water until cold; drain again.

Meanwhile, combine mayonnaise, lemon peel and juice, tarragon, mustard, and 1/2 tsp. each salt and pepper in a food processor. Whirl until smooth.

Combine seafood, watercress, capers, and dressing in a large bowl. Add more salt and pepper to taste. Gently stir in avocado.

Serve on a bed of butter lettuce or as a sandwich in thick, toasted bread.