Prepare the Shrimp and Sauce Base:

1. Prepare the Shrimp: If you haven’t already, peel and devein the shrimp, leaving the tails on for an elegant presentation, if desired. Pat the shrimp dry with paper towels to remove excess moisture.
2. Heat the Olive Oil: In a large skillet or sauté pan, heat the olive oil over medium-high heat.
3. Sauté Garlic: Add the finely chopped or minced garlic to the hot oil. Sauté for 1-2 minutes, or until fragrant and golden, but not burnt. If you’re adding onions, sauté them with the garlic until softened, about 3-4 minutes.

Make the Tomato Sauce:

4. Add the Tomatoes: Pour in the canned diced tomatoes (or fresh tomatoes if using) along with the tomato paste, if desired. Stir to combine. Allow the mixture to simmer for 5-7 minutes, stirring occasionally, so the flavors can meld together. If the sauce is too thick, you can add a splash of water or vegetable broth to loosen it up.
5. Season the Sauce: Add the oregano, red chili flakes (for heat), and season with salt and pepper to taste. Let the sauce simmer for an additional 3-5 minutes. Taste and adjust the seasoning as needed. If you’re adding capers or olives, stir them in at this point for an extra flavor boost.

Cook the Shrimp:

6. Add the Shrimp to the Sauce: Once the tomato sauce has thickened and developed flavor, gently add the shrimp to the pan. Stir to coat the shrimp in the sauce.
7. Cook the Shrimp: Let the shrimp cook in the sauce for 3-5 minutes, or until they turn pink and opaque. Be careful not to overcook the shrimp, as they can become tough and rubbery. Stir occasionally to ensure they cook evenly.

Finishing Touches:

8. Add Lemon Juice and Garnish: Once the shrimp are cooked, remove the pan from heat. Add a squeeze of fresh lemon juice for a touch of brightness, and sprinkle freshly chopped parsley over the top for a pop of color.
9. Serve: Serve the garlic shrimp in tomato sauce immediately, either on its own or with a side of rice, pasta, or crusty bread to soak up the delicious sauce.