01 -
Bring a large pot of salted water to a boil. Add rigatoni and cook until just al dente. Reserve 120 ml of pasta cooking water, then drain the pasta.
02 -
Pat the steak dry with paper towels. Season both sides evenly with Cajun seasoning, kosher salt, and black pepper.
03 -
Heat a large skillet over medium-high heat. Add olive oil and 15 g butter. Sear the steak for 3 to 4 minutes per side for medium-rare doneness. Transfer steak to a plate and let rest.
04 -
Reduce heat to medium. Add remaining 28 g butter to the skillet, then stir in minced garlic and cook for 30 seconds until fragrant.
05 -
Pour beef broth into the skillet and simmer for 1 minute. Add heavy cream and bring to a gentle simmer.
06 -
Whisk in shredded mozzarella and grated Parmesan cheese until the sauce is smooth. Add reserved pasta water gradually to adjust sauce consistency as needed.
07 -
Add the cooked rigatoni to the sauce and toss thoroughly to coat evenly.
08 -
Slice the rested steak against the grain. Return sliced steak to the skillet with the sauce. Add red pepper flakes (if using), fresh parsley, and lemon juice. Stir to combine, adjust seasoning to taste, and serve immediately.