2 tablespoons olive oil
1 small yellow onion, diced
2 cloves garlic, minced
1 (12-ounce) jar roasted red peppers, drained and coarsely chopped
3/4 cup heavy cream
1/2 cup grated Parmesan cheese, plus more for serving
1/2 teaspoon kosher salt
Freshly ground black pepper
1 pound dried pasta, such as fusilli, penne, fettuccine, or linguine
2 tablespoons coarsely chopped fresh basil leaves
Bring a large pot of salted water to a boil. Meanwhile, heat the oil in a medium saucepan over medium-high heat until shimmering. Add the onion and sauté until translucent and soft, 3 to 5 minutes. Add the garlic and sauté for 1 minute more. Remove from the heat.
Stir in the peppers, cream, cheese, salt, and a few grinds of black pepper. Transfer to a stand blender and blend until smooth; set aside. (Alternatively, use an immersion blender right in the saucepan.
Add the pasta to the pot of boiling water and cook until al dente according to package instructions. Reserve 1/4 cup of the pasta water, then drain the pasta. Return the pasta to the pot.
Add the pepper sauce and toss to combine. If needed, add the reserved pasta water a tablespoon at a time to loosen the sauce so that the pasta is evenly coated. Sprinkle with the basil and more Parmesan as desired.