Bring a large pot of salted water to a boil and cook the penne according to package directions until al dente. Drain and set aside.

In a large zip-top bag, combine 3 teaspoons of the Cajun seasoning, 1/4 teaspoon of salt, and 1/4 teaspoon of pepper. Add the chicken pieces, seal the bag, and shake to coat evenly. Set aside.

Heat a large skillet over medium heat and melt 2 tablespoons of the butter.

Add the seasoned chicken to the skillet and cook until browned and cooked through, working in batches if necessary. Transfer the chicken to a plate and set aside.

Melt the remaining 1 tablespoon of butter in the same skillet.

Add the diced onion and bell peppers; cook, stirring frequently, until they begin to soften, about 3 to 5 minutes.

Stir in the heavy cream, smoked paprika, dried basil, garlic powder, the remaining 1 teaspoon of Cajun seasoning, and the remaining 1/4 teaspoon each of salt and pepper. Bring the mixture to a boil, then reduce the heat and simmer until the sauce thickens.

Return the chicken to the skillet. Add the Parmesan cheese and the drained penne, stirring until the cheese is melted and everything is coated with sauce. Serve warm, garnished with fresh parsley if desired.