1. In a nonreactive saucepan, combine 2 cups of water with the onion, garlic, red bell pepper, chiles, vinegar, sugar, peppercorns and allspice. Boil over high heat for 2 minutes, then stir in the shrimp and cook just until pink and loosely curled. Stir in 2 teaspoons salt and the lemon slices, squeezing them a bit. Transfer the shrimp and marinade to a large bowl or wide 2-quart jar and let cool to room temperature. Cover and refrigerate overnight, stirring a few times.
2. Transfer the shrimp to a clean bowl. Strain 3/4 cup of the marinade into a small bowl. Cut 4 of the red pepper strips into small dice. Stir 3/4 teaspoon salt into the strained marinade and whisk in the oil. (Discard the remaining marinade.)
3. Pour the dressing over the shrimp and toss well. Spoon the chilled shrimp onto plates and garnish with the red pepper dice and parsley leaves.
Serve With: Crusty bread, corn bread or biscuits and a cucumber salad.
Notes: Be sure to use large shrimp (about 20 to the pound), which won't become too tangy as they marinate overnight in the spicy brine.