Chef Lindsay Autry's Pickled Shrimp

1 pound medium pink shrimp; shell-on preferably
3 tbsp Old Bay seasoning; divided
2 tsp celery seeds
1 cup extra-virgin olive oil
3 lemons; zested and juiced
1 cup flat-leaf parsley, finely chopped
2 tbsp fresh dill, picked into small pieces
2 tsp crushed red chili flakes
2 cloves garlic, finely chopped
8 dried or fresh bay leaves
2 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.  Remove shrimp from liquid or strain into a colander, and cool on a sheet tray or large platter.  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.