Cook pasta in salted water until al dente. Drain, but save 1/2 cup of the pasta water.
In a large skillet over medium heat, brown the ground beef until no longer pink. Drain excess fat.
Push beef to one side. Add butter to the empty side and melt. Stir in garlic and cook for about a minute until fragrant.
Mix garlic butter into the beef. Add red pepper flakes, salt, and pepper.
Toss in the cooked pasta and a splash of reserved pasta water to bring it all together.
Stir in Parmesan cheese and top with fresh parsley before serving (optional, but hey—it’s pretty).