- 2 tbsp. Old Bay seasoning
- 1 lb. (26–30 count) medium shrimp, peeled and deveined
- 1⁄2 tsp. celery seeds
- 1⁄4 tsp. allspice berries
- 1 cup extra-virgin olive oil
- 1⁄3 cup fresh lemon juice
- 1⁄4 cup packed flat-leaf parsley leaves, finely chopped
- 1 tbsp. kosher salt
- 1⁄2 tsp. crushed red chile flakes
- 2 cloves garlic, finely chopped
- 12 dried bay leaves
- 1⁄2 medium yellow onion, thinly sliced lengthwise
Bring 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.
Finely grind celery seeds and allspice in a spice grinder; transfer to a bowl and stir in oil, juice, parsley, salt, chile flakes, garlic, and bay leaves. In a 1-qt. glass jar, layer shrimp and onions; pour over oil mixture. Cover with lid; chill overnight before serving.