Cook the penne pasta according to package instructions in a large pot of salted boiling water until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes, or until translucent.
Add the minced garlic to the skillet and cook for an additional 1 minute, stirring frequently to prevent burning.
Stir in the chopped roasted red peppers and cook for another 2 minutes.
Pour in the heavy cream and add the Italian seasoning, salt, and pepper. Stir well and bring the mixture to a gentle simmer.
Reduce the heat to low and stir in the grated Parmesan cheese until melted and smooth.
Add the cooked penne pasta to the skillet and toss to coat the pasta evenly with the creamy sauce.
Serve immediately, garnished with fresh basil leaves.