1. Grate 1/2 teaspoon lemon rind from lemon. Squeeze lemon to measure 1 1/2 tablespoons juice. Combine lemon rind, juice, mayonnaise, and green onions in a large bowl. Add shrimp and celery; toss gently.
2. Top each bun with 1 lettuce leaf. Spoon shrimp mixture evenly onto lettuce leaves. Serve immediately.
Serve with: Pear-Kiwi Salad