Peel & devein the shrimp. Run the tip of a sharp knife down the back of a shrimp and remove the dark vein. Repeat with the remaining shrimp. Rinse under cold water. Refrigerate the shrimp until you’re ready to cook.

Sauté the aromatics. Heat the olive oil in a large skillet over medium heat. Add the peppers, onions, and celery. Cook until the vegetables are just tender, stirring frequently to prevent sticking. Add the garlic and cook for an additional 1 minute.

Add the tomatoes and seasonings. Add the crushed and diced tomatoes along with the Cajun seasoning, oregano, cayenne, and red pepper flakes, if using. Adjust the heat to suit your taste. Add salt and pepper to taste. Bring to a simmer. Reduce the heat to low and cook for 20 minutes, stirring frequently.

Cook the shrimp. Meanwhile, place the shrimp in a saucepan and cover with water. Bring to a rolling boil and cook just long enough for the shrimp to turn pink. Remove from heat and drain.

Finish the dish. Add the shrimp to the sauce and continue cooking for about 5 minutes. Serve with hot cooked rice.