Bring a large pot of salted water to a boil and add the penne pasta. Cook the pasta according to the package instructions until al dente, about 9–10 minutes. Once cooked, drain the pasta and set it aside to allow any remaining water to evaporate.

While the pasta cooks, rub Cajun seasoning on both sides of the boneless, skinless chicken fillets. Set the seasoned chicken aside.

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Once shimmering, add the seasoned chicken fillets. Cook for about 6–7 minutes on each side until golden brown and cooked to an internal temperature of 165°F. Remove chicken and let it rest before slicing.

In the same skillet, add sliced onion and bell peppers over medium heat. Sauté for about 3 minutes until softened. Add minced garlic and cook for an additional 30 seconds.

Pour in 1 cup of heavy cream and 1 cup of chicken broth. Stir in 1 cup of grated Parmesan cheese and mix until melted. Let it simmer for 3–4 minutes to thicken slightly.

Once thickened, reintroduce the sliced chicken and drained pasta back into the skillet. Toss together gently to ensure everything is well-coated with the sauce. Adjust with salt and pepper to taste.

Serve immediately, garnished with extra Parmesan cheese or freshly chopped parsley if desired.