Begin by boiling the fettuccine according to the package instructions. Once al dente, drain and set aside.

In a large skillet, heat olive oil over medium heat. Add the sliced chicken breast and cook until it is nicely browned, seasoning with salt and pepper.

Once the chicken is browned, add in the sliced bell peppers, chopped onion, and minced garlic. Sauté until the vegetables are tender and the garlic is fragrant, about 5 minutes.

Reduce the heat slightly, then stir in the heavy cream, grated Parmesan cheese, Cajun seasoning, and red pepper flakes. Cook until the sauce starts to thicken.

Add the cooked fettuccine to the skillet, tossing until the pasta is evenly coated with the sauce. Taste and adjust seasoning if necessary.

Garnish with chopped parsley and extra Parmesan cheese if desired. Serve immediately.