Step 1: Cook the Pasta
Bring a large pot of salted water to a boil. Add the linguine and cook until al dente according to package instructions. Reserve about ½ cup of the pasta water in case you need to thin the sauce later. Drain the pasta and set it aside.

Step 2: Sear the Steak
In a large skillet over medium-high heat, melt 2 tablespoons of butter. Add the steak strips to the skillet in a single layer (you may need to do this in batches to avoid overcrowding). Sprinkle with Cajun seasoning, red pepper flakes (if using), salt, and pepper. Sear for 3–4 minutes on each side until browned and cooked through. Remove the steak from the pan and set aside.

Step 3: Make the Garlic Butter Base
Lower the heat to medium. In the same skillet, add the remaining 2 tablespoons of butter and the minced garlic. Sauté for 1–2 minutes until the garlic is fragrant but not browned.

Step 4: Build the Creamy Parmesan Sauce
Pour in the heavy cream and let it simmer gently for about 2 minutes. Gradually whisk in the Parmesan cheese until fully melted and the sauce turns smooth and creamy. Taste and adjust salt and pepper as needed.

Step 5: Combine and Serve
Return the cooked linguine to the skillet, tossing it in the creamy sauce until well coated. If the sauce feels too thick, add a bit of the reserved pasta water until it reaches your preferred consistency. Add the seared steak back into the pan and gently toss everything together. Garnish with chopped fresh parsley and extra Parmesan, then serve immediately.