Begin by bringing a large pot of salted water to a rolling boil. Add the rigatoni pasta and cook until al dente, about 8-10 minutes. Drain and set aside.

Season the sliced steak with salt and pepper. In a skillet, melt 2 tablespoons of butter over medium-high heat and add the steak. Cook for 3-4 minutes until browned, then remove from skillet.

Reduce heat to medium, add the remaining butter, and sauté the minced garlic and red pepper flakes for 1 minute until fragrant.

Pour in the beef broth, simmer for 2-3 minutes to reduce slightly.

Stir in the heavy cream and simmer for another 2-3 minutes until thickened.

Return the cooked steak to the skillet along with the rigatoni and grated Parmesan. Toss to coat and heat through for about 2-3 minutes.

Serve warm, garnished with fresh parsley.