Bring a large pot of salted water to a boil. Add the tortellini and cook according to the package directions. Typically fresh ravioli will cook in 3-5 minutes.
Meanwhile, heat the olive oil in a large skillet. Add the red pepper and onion and sauté until somewhat soft. Add the red pepper flakes and tomatoes. Cook until the tomatoes start to wilt and release their juices.
Drain the pasta and add it to the pan with the vegetables, and toss to coat.
Stir in the pesto and Parmesan cheese. Cook until heated through, 1-2 minutes.