Step 1: Bring a large pot of salted water to a boil and cook rigatoni according to package directions until al dente. Drain and set aside.
Step 2: While pasta cooks, season steak strips with salt and pepper.
Step 3: Heat olive oil in a large skillet over medium-high heat. Add steak and cook for 3-4 minutes until browned. Remove steak and set aside.
Step 4: In the same skillet, melt butter over medium heat. Add minced garlic and cook for 1-2 minutes until fragrant.
Step 5: Stir in heavy cream and bring to a gentle simmer. Cook for 2-3 minutes until slightly thickened.
Step 6: Add Parmesan cheese and stir until melted and smooth. Season with salt, pepper, and red pepper flakes if using.
Step 7: Return cooked steak to the skillet along with the drained rigatoni. Toss to coat everything in the sauce.
Step 8: Stir in chopped parsley and serve immediately.