01 - Bring a large pot of salted water to a boil. Cook the cheese tortellini according to package instructions. Drain and set aside, reserving 1/4 cup pasta water.
02 - Season the steak strips with salt and pepper.
03 - Heat 1 tablespoon butter in a large skillet over medium-high heat. Add the steak in a single layer and cook for 1–2 minutes per side until browned but still tender. Remove steak and set aside.
04 - Reduce heat to medium. Add remaining 2 tablespoons butter to the skillet. Add garlic and sauté for 1 minute until fragrant.
05 - Stir in the heavy cream and bring to a gentle simmer. Add Parmesan cheese and red pepper flakes, stirring until cheese melts and sauce thickens, about 2–3 minutes.
06 - Add spinach and cook until wilted, about 1 minute.
07 - Return steak and any juices to the skillet. Add drained tortellini and toss to coat everything in the sauce. If sauce is too thick, add a splash of reserved pasta water. Sprinkle with fresh parsley and extra Parmesan before serving.