Zest of 1⁄2 lemon
1 tablespoon Tabasco sauce
For Shrimp: Bring water to a boil in a large stock pot.
Stir in Old Bay, cayenne pepper, and the juice from 1⁄2 lemon until well blended.
Add in raw shrimp and turn down heat.
Simmer for about 2 minutes, or until shrimp is opaque/pink and the edges just start to curl.
Remove from heat, strain, and place on ice to halt the cooking process.
For Cocktail Sauce: In a medium mixing bowl, combine the leftover lemon juice, tomato purée, tomato paste, horseradish, lemon zest, and Tabasco sauce.
Whisk until well blended and refrigerate along with the shrimp.
Best served chilled with shrimp displayed evenly on a large platter, around a small serving dish of cocktail sauce centered in the middle, with lemon slices to garnish.