Preheat your oven’s broiler or set the oven to 450°F (230°C). Place the red bell peppers whole on a baking sheet. Roast them for about 15-20 minutes, turning occasionally, until the skin is charred and blistered all over. Transfer the peppers to a bowl, cover with plastic wrap or a kitchen towel, and let them steam for 10 minutes to make peeling easier.
While the peppers are steaming, bring a large pot of salted water to a boil. Add the rigatoni and cook according to package instructions until al dente (approximately 11-13 minutes). Reserve about ½ cup of pasta water, then drain the rigatoni and set aside.
Once the peppers are cool enough to handle, peel off the charred skin, remove the seeds, and roughly chop the flesh. Transfer the roasted peppers to a blender or food processor and puree until smooth. Set aside.
Heat the olive oil in a large skillet over medium heat. Add the chopped onion and sauté for 3-4 minutes until translucent. Add the minced garlic and cook for another 1 minute until fragrant, taking care not to burn it.
Lower the heat and stir in the roasted red pepper puree, heavy cream, Italian seasoning, salt, and pepper. Let the sauce simmer gently for 5 minutes to thicken slightly.
Remove the skillet from heat. Stir in the grated Parmesan cheese until melted and the sauce is creamy and smooth. If too thick, add a splash of reserved pasta water to loosen.
Add the cooked rigatoni to the skillet and toss well to coat every piece with the sauce. Warm through on low heat for 1-2 minutes.
Serve hot, garnished with fresh basil leaves. Enjoy immediately for best flavor and texture.
