1 pound medium pink shrimp; shell-on preferably
3 tbsp. Old Bay seasoning; divided
½ tsp. celery seeds
1 cup extra-virgin olive oil
3 lemons; zested and juiced
¼ cup flat-leaf parsley leaves, finely chopped
2 tbsp. fresh dill, picked into small pieces
½ tsp. crushed red chile flakes
2 cloves garlic, finely chopped
12 dried bay leaves
½ medium yellow onion, thinly sliced lengthwise
Bring 2 tbsp. Old Bay and 8 cups water to a boil in a 4-qt. saucepan; add shrimp, reduce heat to low, and cook until shrimp are pink, about 2 minutes. Drain and transfer to bowl of ice water to chill; drain again. Peel and devein the shrimp if using shell-on.
Combine all remaining ingredients, including 1 tbsp. Old Bay, in a mixing bowl and stir to combine. Add the chilled shrimp and toss to mix well.
Store shrimp and liquid in a glass jar and refrigerate overnight or up to 3 days.