01 - Bring a large pot of salted water to a boil. Add the penne pasta and cook until al dente according to package directions. Drain well, reserving 1/2 cup of the pasta cooking water, and set aside.
02 - Slice each chicken breast in half horizontally to create thinner cutlets. Rub both sides evenly with 1 tablespoon of Cajun seasoning, pressing gently to adhere.
03 - Heat olive oil in a large skillet over medium-high heat. Add the seasoned chicken and cook for 4 to 5 minutes per side until golden brown and cooked through. Transfer to a plate and let rest for 2 minutes before slicing into strips.
04 - In the same skillet, reduce heat to medium and melt the butter. Add the diced onion and sauté for 2 minutes until softened. Add the minced garlic and cook for 30 seconds until fragrant.
05 - Stir in the sliced red and yellow bell peppers. Cook for 3 to 4 minutes until slightly softened but still retaining some crunch.
06 - Pour in the heavy cream and chicken broth. Add the remaining teaspoon of Cajun seasoning and bring to a gentle simmer, stirring constantly.
07 - Stir in the grated Parmesan cheese and cook for about 2 minutes until fully melted and the sauce has thickened slightly. Taste and adjust seasoning with salt and black pepper as needed.
08 - Add the cooked penne pasta and sliced chicken to the skillet. Toss everything together until evenly coated with the sauce. If the sauce is too thick, add a splash of the reserved pasta water. Serve hot, garnished with fresh chopped parsley and additional Parmesan cheese if desired.