In a bowl, toss the sliced chicken breasts with Cajun seasoning. Let it marinate for at least 20 minutes.
In a large pot of salted boiling water, cook the fettuccine or linguine according to package instructions until al dente. Drain and set aside, reserving 1/2 cup of pasta water.
In a large skillet, heat olive oil over medium heat. Add the chopped onion, sliced red and yellow bell peppers, and cook until they are softened, about 5 minutes.
Stir in the minced garlic and sauté for an additional minute until fragrant.
Push the vegetables to one side of the skillet and add the marinated chicken. Cook until browned and cooked through, about 5-7 minutes.
Once the chicken is cooked, pour in the chicken broth and heavy cream. Bring to a simmer, stirring to combine and allow the sauce to thicken slightly.
Add the cooked pasta to the skillet, tossing gently to coat in the sauce. If the sauce is too thick, add some reserved pasta water as needed to reach desired consistency.
Stir in the grated Parmesan cheese until it melts into the sauce. Season with salt and pepper to taste.
Divide the Cajun Chicken Pasta among plates and garnish with chopped fresh parsley.
Notes
Adjust the spice level by varying the amount of Cajun seasoning.