01 - Heat 1 tablespoon of butter in a large skillet over medium-high heat. Add the steak pieces, season with salt and black pepper, and sear for 2 to 3 minutes per side until well-browned. Remove the steak from the pan and set aside.
02 - In the same skillet, add the remaining tablespoon of butter. Stir in the minced garlic and crushed red pepper flakes, sautéing for 1 to 2 minutes until the garlic is fragrant but not browned.
03 - Add rotini pasta to the skillet along with 2 1/2 to 3 cups of water or broth. Stir to combine, bring to a boil, then reduce to a simmer and cook uncovered for 9 to 11 minutes, stirring occasionally until the pasta is al dente and most of the liquid is absorbed.
04 - Pour in heavy cream and add grated Parmesan cheese to the skillet. Stir well and allow the sauce to simmer for 2 to 3 minutes, until thickened to your liking.
05 - Return the seared steak and any juices to the pan. Toss gently to coat with the sauce. Adjust seasoning with additional salt and black pepper if needed. Garnish with chopped parsley if desired and serve immediately.