Bring a large pot of salted water to a boil. Cook pasta according to package instructions until al dente. Drain and set aside, reserving about 1/2 cup pasta water.
In a large skillet over medium heat, melt 2 tbsp butter. Add ground beef, season with salt and pepper, and cook until browned. Drain excess grease if needed. Remove beef and set aside.
In the same skillet, melt remaining 2 tbsp butter. Add onion and cook until softened, about 3 minutes. Stir in minced garlic, Italian seasoning, and red pepper flakes. Cook until fragrant, about 1 minute.
Pour in beef broth and let simmer for 2-3 minutes. Stir in heavy cream and Parmesan cheese until creamy. Return the cooked beef to the skillet and mix well.
Add the drained pasta to the skillet, tossing to coat in the sauce. If needed, stir in a splash of reserved pasta water to loosen the sauce.
Stir in fresh parsley. Taste and adjust with more salt or pepper if needed. Garnish with extra Parmesan and parsley before serving.
Notes
Refrigerate leftovers up to 3-4 days; freeze for up to 2 months and thaw overnight before reheating. Reheat with a splash of broth or water to revive the sauce. Ground turkey, chicken, or Italian sausage can replace the beef.
Keyword creamy beef pasta, dinner recipe, garlic butter beef pasta