In a large skillet, heat the olive oil over medium heat. Once hot, add the chopped onion and sauté for about 5 minutes, until it becomes translucent and soft.

Add the minced garlic to the skillet and cook for an additional 1-2 minutes, stirring frequently, until fragrant. Be careful not to burn the garlic.

Pour in the crushed tomatoes and stir to combine. Add the dried oregano, red pepper flakes (if using), salt, and pepper. Bring the mixture to a simmer and let it cook for about 10 minutes, allowing the flavors to meld together.

Once the sauce has thickened slightly, add the shrimp to the skillet. Stir gently to coat the shrimp in the sauce. Cook for 3-5 minutes, or until the shrimp are pink and opaque, ensuring they are cooked through but not overcooked.

Remove the skillet from heat and garnish with chopped fresh parsley. Serve with lemon wedges on the side to squeeze over the top for added brightness.