Cook the pasta according to package instructions. Drain and set aside, reserving some pasta water.
Heat olive oil in a large skillet over medium heat. Season the shrimp with salt and pepper, then add them to the skillet. Cook for 3 minutes per side until they turn pink and opaque. Remove the shrimp from the skillet and set aside.
In the same skillet, add red onions and sauté for about 5 minutes or until soft and fragrant; stir in minced garlic and red pepper flakes. Sauté for a minute and add in chopped tomatoes. Cook until tomatoes are tender.
Stir in the cooked pasta and Spicy Garlic-Parm sauce to the skillet. Toss well to coat the pasta with the sauce.
Return the cooked shrimp to the skillet, mixing them in with the pasta.
If needed, add a bit of reserved pasta water to adjust the consistency of the sauce.
Serve the pasta and shrimp garnished with fresh chopped parsley.