Cook the fettuccine: Begin by bringing a large pot of salted water to a boil. Add 12 oz fettuccine pasta and cook according to package instructions until al dente, about 8-10 minutes. Drain and set aside while reserving a cup of the pasta water.
Prepare the steak: In a medium bowl, season 1 lb thinly sliced steak with 1 tbsp Cajun seasoning and 1/2 tsp smoked paprika. Make sure the steak is well coated.
Sear the steak: Heat 2 tbsp unsalted butter in a large skillet over medium-high heat. Once melted and bubbling, add the seasoned steak. Sear for approximately 2-3 minutes on each side, or until cooked through and golden. Remove the steak from the skillet and set it aside on a plate.
Sauté the garlic and prepare the sauce: In the same skillet, add 4 cloves minced garlic and sauté for about 1 minute until fragrant. Pour in 2 cups heavy cream and bring to a gentle simmer. Gradually whisk in 1 cup grated Parmesan cheese until the sauce thickens, about 3-5 minutes. Season with salt and pepper to taste.
Toss the pasta and steak: Add the drained fettuccine to the skillet with the creamy sauce, tossing to coat evenly. Incorporate the seared steak, mixing until everything is well combined and heated through.
Serve the dish: Plate the pasta and steak, garnishing with chopped parsley. Enjoy your delicious Creamy Cajun steak Alfredo!