Bring salted water to a boil, cook rotini 8–9 minutes, drain, and reserve ½ cup pasta water.
Pat steak dry and season with Cajun seasoning, garlic powder, paprika, salt, and pepper.
Heat oil and butter in skillet over medium-high. Sear steak 1–2 minutes per side until browned. Set aside.
Add butter and garlic to skillet; cook until fragrant.
Stir in cream and milk; simmer gently.
Whisk in cream cheese until smooth, then add Parmesan and mozzarella.
Toss in rotini; coat with sauce. Add steak and stir gently.
Garnish with parsley and enjoy hot.
