Cook tortellini according to package directions. Drain and set aside.
- Heat olive oil in a large skillet over medium-high heat. Add sliced steak and cook until browned. Remove and set aside.
- In the same skillet, sauté onions and bell peppers until caramelized, about 6–8 minutes. Add garlic and cook for 1 more minute. Remove veggies from skillet.
- Melt butter in the skillet, whisk in flour to form a roux, and cook 1–2 minutes.
- Slowly whisk in milk or half-and-half. Cook until thickened, 4–5 minutes.
- Stir in provolone cheese until melted and smooth. Season with salt, pepper, and crushed red pepper flakes if using.
- Return steak, onions, and peppers to the skillet. Add tortellini and toss until coated in sauce.
- Serve hot, garnished with extra provolone or parsley.