Start by bringing a large pot of salted water to a rolling boil over high heat.

Add the spaghetti and cook according to package instructions until al dente, about 8 to 10 minutes.

Drain the pasta well in a colander and set it aside, reserving a bit of pasta water in case you need to thin the sauce later.

While the pasta cooks, toss the diced beef with Cajun seasoning in a mixing bowl until evenly coated.

Heat a large skillet over medium-high heat and add a tablespoon of butter.

Once the butter is melted and bubbling, add the seasoned beef. Sear the beef for about 3–4 minutes, stirring occasionally until nicely browned and just cooked through.

Remove the beef from the skillet and set it aside.

In the same skillet, add another tablespoon of butter and decrease the heat to medium.

Toss in the freshly minced garlic and sauté for about 1 minute, or until fragrant.

Pour in the heavy cream, stirring continuously, and bring it to a gentle simmer.

Add the cream cheese, mozzarella, and Parmesan, stirring until melted and smooth, about 3–5 minutes.

Return the cooked beef and spaghetti to the skillet with the creamy sauce. Toss everything together thoroughly.

Garnish generously with chopped parsley before serving.