Season shrimp with the lemon zest, paprika, parsley flakes, hot sauce and onion powder. Cover and refrigerate until ready to use.
Brown the Cajun trinity of onion, bell pepper and celery in the oil or butter in a 9-inch cast iron skillet over medium heat.
Stir the stewed tomatoes, tomato sauce, broth, bay leaf, parsley flakes, paprika, hot sauce and SP&C to taste into the skillet.
Reduce heat to low. Simmer for about 40 minutes, or until the sauce turns dark crimson.
Add the seasoned shrimp to the skillet. Cook for an additional 5 to 10 minutes, or until shrimp turn opaque and are well-incorporated into the Creole sauce.
Rest for 10 minutes, or until the shrimp Creole gravy thickens. (See notes)
Serve as is, or with rice or cauliflower rice.
The shrimp Creole gravy will be very watery at the end, due to the shrimp releasing their liquids upon cooking. Letting the skillet rest for at least 10 minutes allows the gravy to thicken perfectly, and also melds all of the individual flavors of the dish together.