Bring a large pot of salted water to a rolling boil. Add the spaghetti and cook until al dente, about 8-10 minutes. Drain and set aside.

Toss diced sirloin or ribeye steak with Cajun seasoning. Heat a skillet over medium-high heat with butter, sear the beef until browned, about 3-4 minutes, then set aside.

In the same skillet, add butter and reduce heat. Sauté minced garlic for about 1 minute until fragrant.

Pour in the heavy cream, and stir. Add cream cheese, mozzarella, and parmesan, mixing until melted and smooth, about 3-5 minutes.

Return spaghetti and beef to the skillet, tossing until well-coated with the sauce for about 2-3 minutes.

Garnish with chopped parsley and serve hot, with extra cheese and Cajun seasoning on the side if desired.