Bring a large pot of salted water to a boil and cook fettuccine according to package directions until al dente; drain and set aside.
While the pasta cooks, heat 2 tablespoons of the oil from the sun-dried tomato jar in a large skillet over medium heat.
Add the chopped sun-dried tomatoes, minced garlic, and red pepper flakes and sauté for about 1 minute until fragrant.
Sprinkle in the flour and cook, stirring constantly, for 2 minutes to remove the raw flour taste.
Reduce heat to low and slowly whisk in the chicken broth until smooth.
In a small bowl, whisk the cornstarch into the milk until dissolved, then add the mixture to the skillet along with tomato paste, dried basil, dried parsley, onion powder, oregano, salt, and pepper.
Bring the sauce to a gentle simmer and cook, stirring occasionally, until it thickens slightly, about 5 minutes; keep the sauce pourable but thickened.
Lower the heat to low and stir in the cubed reduced-fat cream cheese until melted and smooth, then add the grated Parmesan and stir until melted.
Stir in the shredded mozzarella until melted, then add the drained fettuccine and toss until the pasta is evenly coated with the sauce.
Taste and adjust seasoning with more salt, pepper, or red pepper flakes if desired, then serve topped with additional freshly grated Parmesan and fresh basil.