Start by bringing 5 quarts of water to a vigorous boil in a large pot. Squeeze the juice of one lemon into the water and stir in a generous amount of salt to season.

Once the water is boiling, add the shrimp and cook them for 2-3 minutes, until they turn a lovely pink color and are opaque.

Remove the pot from heat and swiftly drain the shrimp in a colander. Transfer the shrimp to an ice bath filled with cold water for 5 minutes.

In a medium-sized mixing bowl, combine mayonnaise, lemon zest, and juice from the remaining lemon half. Add Dijon mustard, garlic powder, salt, black pepper, fresh dill, chives, and celery. Whisk together until smooth.

Pat the chilled shrimp dry and add them to the dressing. Gently toss until the shrimp are well coated.

To serve, arrange butter lettuce leaves on plates and spoon the dressed shrimp mixture on top.