Boil 2 quarts of salted water in a large pot. Add lemon slices, garlic, bay leaf, and Cajun seasoning. Once boiling, add shrimp and cook for about 3 minutes until pink and opaque. Remove from heat.

Transfer the poached shrimp to a plate using a slotted spoon and let cool for a few minutes. Refrigerate for about 15 minutes until chilled.

In a large mixing bowl, combine the chilled shrimp, diced red bell pepper, chopped celery, and sliced green onions.

In a small bowl, mix the mayonnaise, lemon juice, dill, salt, and pepper until smooth.

Pour the dressing over the shrimp and vegetable mixture, folding gently until well coated. Cover with plastic wrap and refrigerate for at least one hour.

Once chilled, stir gently and serve on buttered rolls, in lettuce cups, or with crackers.