Start by patting the steak cubes completely dry. This matters more than you think. Toss them in a bowl with the Cajun seasoning and make sure every piece is coated.

Heat a heavy skillet over medium-high heat with the olive oil and half the butter. Once hot, add the steak in a single layer. Don’t crowd the pan. Let the steak sear for about 2 minutes per side until browned. You’re aiming for medium-rare since it will cook more later. Remove steak and let it rest.

While the steak rests, bring a large pot of well-salted water to a boil. Cook the rigatoni 1 minute less than the package directions. Before draining, reserve about 1/2 cup of pasta water, then drain.

Using the same skillet, lower the heat to medium-low and melt the remaining butter. Add the garlic and cook for about 30 seconds, just until fragrant.

Pour in the cream and scrape up all the browned bits from the pan. Reduce heat to low and slowly whisk in the Parmesan cheese, adding it in small amounts until smooth.

If the sauce feels too thick, add reserved pasta water a little at a time until it coats the back of a spoon.

Add the pasta and steak back into the skillet and gently toss everything together. If using mozzarella, stir it in now until melted.

Taste and adjust seasoning with salt, pepper, or more Cajun spice. Serve immediately.