01 - Cook penne pasta in a large pot of salted boiling water according to package directions until al dente. Drain and set aside, reserving 1/2 cup of pasta cooking water.
02 - Slice chicken breasts horizontally through the center to create thinner cutlets. Coat both sides evenly with 1 tablespoon Cajun seasoning, pressing gently to adhere.
03 - Heat olive oil in a large skillet over medium-high heat. Add seasoned chicken and cook for 4-5 minutes per side until golden brown and cooked through. Remove from skillet, let rest for 2 minutes, then slice into strips.
04 - Melt butter in the same skillet over medium heat. Add diced onion and sauté for 2 minutes until translucent. Add minced garlic and cook for 30 seconds until fragrant.
05 - Stir in sliced red and yellow bell peppers. Cook for 3-4 minutes until slightly softened but still retaining some crunch.
06 - Pour in heavy cream and chicken broth. Add remaining teaspoon of Cajun seasoning. Bring mixture to a gentle simmer, stirring occasionally.
07 - Stir in grated Parmesan cheese and cook for 2 minutes until melted and sauce has thickened slightly. Season with salt and black pepper to taste.
08 - Add drained pasta and sliced chicken strips to the skillet. Toss everything together until evenly coated with sauce. If too thick, thin with reserved pasta water. Serve hot, garnished with chopped fresh parsley and additional Parmesan if desired.