Boil a large pot of salted water and cook spaghetti according to package instructions until al dente, about 8-10 minutes. Reserve ½ cup of pasta water, then drain spaghetti.

In a large skillet, heat 2 tablespoons of olive oil over medium-high heat. Add lean ground beef seasoned with Cajun seasoning and sear for about 5-7 minutes until browned.

In the same skillet, reduce heat to medium and melt 2 tablespoons of unsalted butter. Add 3 minced garlic cloves and sauté for 1-2 minutes until fragrant.

Slowly pour in 1 cup of heavy cream and bring to a simmer over medium-low heat for about 3-4 minutes.

Gradually stir in ½ cup of Parmesan, 1 cup of mozzarella, and 1 cup of cheddar until cheese melts and sauce is smooth.

Add drained spaghetti to the sauce, tossing to coat. Adjust consistency with reserved pasta water if needed. Cook over low heat for 1-2 minutes.

Fold the cooked beef back into the skillet, simmer for another 2-3 minutes to reheat.

Serve on warm plates, garnishing with additional Parmesan, pepper, and parsley.