Boil a large pot of salted water over high heat. Add fettuccine or penne pasta and cook according to package instructions until al dente, about 8-10 minutes. Drain and reserve ½ cup pasta water.

Season steak with salt and black pepper. Heat skillet over medium-high heat with olive oil. Sear steak for 2-3 minutes on each side. Remove from skillet and let rest.

Lower skillet heat to medium. Melt unsalted butter in the steak juices and sauté minced garlic for 1-2 minutes until fragrant.

Add beef broth, scraping skillet to release flavor bits. Simmer for about 2 minutes.

Stir in heavy cream and Parmesan cheese until well mixed and sauce thickens, about 3-4 minutes. Add crushed red pepper flakes if desired.

Toss drained pasta in the sauce. Adjust consistency with reserved pasta water if needed. Add sliced steak back into the skillet.

Plate the dish and garnish with chopped parsley. Optionally, add more grated Parmesan before serving.