Bring a large pot of salted water to a rolling boil over high heat. Add rigatoni pasta and cook according to package instructions until al dente, usually about 10-12 minutes. Drain the pasta and set aside.

While the pasta cooks, season sliced steak with salt and pepper. In a skillet, melt 2 tablespoons of butter over medium-high heat. Add the steak, cooking for 3-4 minutes until browned. Remove and set aside.

In the same skillet, reduce heat and add remaining butter. Once melted, add minced garlic and red pepper flakes. Sauté for about 1 minute until garlic is fragrant and lightly golden.

Pour in beef broth and bring to a simmer for 2-3 minutes. Stir in heavy cream and simmer for another 2-3 minutes until slightly thickened.

Return steak to skillet, add drained rigatoni, and grated Parmesan cheese. Toss gently to coat the pasta in the sauce. Heat through for a minute.

Remove from heat and garnish with chopped parsley. Serve hot and enjoy!