MAKE the dressing by adding a 1/2 cup mayonnaise, 1 tsp. lemon zest, and 3 tbsp. lemon juice, 1 tbsp. compatible Dijon mustard, 1 clove garlic, 1/4 tsp. Kosher salt, 1/8 tsp. black pepper to a small bowl. Whisk until well combined and set aside.
ADD water and 1 tbsp. Kosher salt to a 4- or 5-quart pot and bring to a rolling boil. Once boiling, carefully drop in shrimp and set a timer for 2 minutes. Once the timer goes off, drain the shrimp and run cold water over them to stop the cooking.
CHOP the shrimp into 1/2-inch pieces and add to a large bowl with cucumber, celery, green onions, and fresh dill. Toss to combine.
POUR dressing over the shrimp and cucumber mixture and fold in to evenly coat.
SERVE salad with avocado halves or lettuce leaves to make lettuce cups. Store leftovers in an air-tight container in the refrigerator for up to three days.
