Bring a large pot of salted water to a boil and cook the rigatoni until al dente. Reserve about ½ cup of pasta water, then drain and set aside.

Season the steak tips evenly with Cajun seasoning, salt, and pepper.

Heat olive oil in a large skillet over medium-high heat. Add the steak in a single layer and sear for 3–4 minutes per side until browned and cooked to your liking. Remove from the skillet and set aside.

In the same skillet, reduce heat to medium and melt the butter. Add the minced garlic and cook for about 30 seconds until fragrant.

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

Gradually add the Parmesan cheese (and mozzarella if using), stirring until melted and smooth.

Add a splash of reserved pasta water if needed to loosen the sauce.

Stir in the cooked rigatoni until evenly coated.

Add the steak tips back to the skillet and gently toss to combine and warm through.

Serve immediately with optional garnishes.