Step 1: Bring a large pot of salted water to a boil. Cook the rigatoni until just al dente, then drain. Save about ½ cup of pasta water for later. Set aside.

Step 2: Pat the steak tips dry with paper towels. This step ensures a good sear. Season generously with salt, black pepper, and Cajun seasoning if you’re using it.

Step 3: Heat olive oil and 2 tablespoons butter in a heavy skillet over medium-high heat. When the butter foams, add the steak tips in a single layer. Sear for 2–3 minutes per side until golden brown with crispy edges. Transfer to a plate, tent with foil, and let rest.

Step 4: Lower the heat to medium. Add the remaining butter to the skillet and sauté the minced garlic for 1 minute until fragrant, scraping up any browned bits from the bottom of the pan.

Step 5: Pour in heavy cream and milk, whisking to combine. Let the mixture simmer gently for 2–3 minutes.

Step 6: Stir in mozzarella and Parmesan a little at a time, mixing until smooth and creamy. Add Italian seasoning, salt, and pepper to taste. If the sauce thickens too much, stir in a splash of reserved pasta water.

Step 7: Add the rigatoni to the skillet and toss until every tube is coated in the glossy sauce. Simmer for 1–2 minutes to allow the pasta to absorb the flavors.

Step 8: To serve, spoon the rigatoni onto one side of a large platter and arrange the steak tips on the other. Drizzle the garlic butter pan juices over the steak. Garnish with parsley and red pepper flakes if desired.