Bring a large pot of salted water to a boil. Cook rigatoni according to package instructions until al dente. Drain and set aside.
Heat olive oil in a large skillet over medium heat. Add the halved grape tomatoes and cook for about 5 minutes until they start to soften and release their juices.
Add the chopped onion and sauté until translucent, about 3–4 minutes. Stir in the minced garlic and crushed red pepper flakes; cook for 30 seconds until fragrant.
Pour in the canned San Marzano tomatoes with their juices. Use a spoon to break them up slightly. Let the sauce simmer for 10–15 minutes, stirring occasionally.
Stir in the heavy cream and grated Parmesan cheese. Season with salt and garlic powder. Simmer for another 2–3 minutes until the sauce is creamy and well combined.
Add the cooked rigatoni to the sauce and toss to coat evenly. Cook together for 1 minute.
Serve and enjoy!