Cook fettuccine pasta according to package instructions. Drain and set aside.
Slice chicken breasts into thin strips and season with Cajun seasoning.
In a large skillet over medium heat, add olive oil and cook chicken until browned and cooked through. Remove and set aside.
In the same skillet, melt butter and sauté bell peppers and red onion for 4–5 minutes until tender.
Add garlic and cook for 1 more minute.
Pour in heavy cream and chicken broth. Stir well and bring to a simmer.
Add Parmesan cheese, and stir until the sauce is creamy. Season with salt and pepper to taste.
Return the cooked chicken and pasta to the skillet. Toss until everything is evenly coated with the sauce.
Garnish with parsley and serve hot.