Heat 1 tablespoon of the olive oil in a large deep skillet over medium-high heat. Add the shrimp, season with salt and pepper, and sauté just until they start to turn pink, 2 minutes. Remove the shrimp with a slotted spoon to a plate and set aside.
Return the skillet to medium-high heat and add the remaining 1 tablespoon olive oil. Add the onion and bell pepper and sauté until they start to soften, 2 minutes. Add the garlic and sauté until you can smell it, 1 minute more. Add the tomato sauce, tomato paste, oregano, chili powder, and red pepper flakes, if using. Cook, stirring occasionally, to blend the flavors, 5 minutes. Season with salt and pepper. Stir in the olives if using, the parsley, and the reserved shrimp and cook until the shrimp are cooked through, another 2 minutes.