1. Pat and season chicken: Pat chicken dry and coat all over with Cajun seasoning; set aside while you boil water.

2. Cook rotini: Boil in well-salted water until al dente; reserve 1/2 cup pasta water, then drain.

3. Sear chicken: Heat olive oil in a large skillet over medium-high; sear chicken 4 to 5 minutes per side until golden and 165 F. Transfer to a board to rest.

4. Start Alfredo base: Lower heat to medium; add butter to the same skillet. Saute garlic 30 seconds until fragrant.

5. Make it creamy: Stir in heavy cream; simmer gently 2 to 3 minutes. Season with salt and pepper.

6. Melt cheeses: Reduce heat to low; whisk in Parmesan, then mozzarella until smooth and glossy. Loosen with pasta water as needed.

7. Sauce the pasta: Add drained rotini; toss until every spiral is coated. Add cayenne for heat and lemon juice for brightness if desired.

8. Slice chicken: Cut rested chicken into strips; return to the skillet or arrange over the pasta.

9. Finish and serve: Garnish with parsley and extra Parmesan; serve hot.