Pat the chicken dry. Season both sides with 1 tablespoon Cajun seasoning, salt, and pepper.

Heat the olive oil in a large skillet over medium-high until shimmering. Add the chicken and cook 6-7 minutes per side until a deep golden crust forms and the internal temperature reaches 165°F (74°C). Transfer to a plate to rest, then slice.

Bring a large pot of salted water to a boil. Add the pasta and cook according to package directions until al dente. Reserve ½ cup pasta water, drain the pasta, and set aside.

In the same skillet, lower heat to medium and melt the butter. Add the minced garlic and sauté 30-45 seconds until fragrant.

Stir in the additional 1 tablespoon Cajun seasoning and smoked paprika to toast briefly. Pour in the heavy cream and chicken broth, whisking to combine. Let the sauce simmer gently 3-5 minutes until it thickens slightly.

Whisk in the Parmesan until smooth. If the sauce is too thick, add reserved pasta water a splash at a time to reach desired consistency. Taste and adjust salt, pepper, and a squeeze of lemon if needed.

Add the drained pasta and sliced chicken to the skillet. Toss everything until the pasta is well coated and heated through. Sprinkle with parsley and red pepper flakes if using.