Cook the fettuccine in a large pot of salted boiling water according to package instructions, about 8-12 minutes, until al dente. Reserve a cup of pasta water, then drain.

In a large skillet, heat olive oil over medium-high heat. Add chicken and sprinkle with Cajun seasoning. Cook for 6-8 minutes until chicken reaches 165°F and is golden.

Reduce the heat to medium-low, pour in heavy cream, and simmer. Gradually whisk in Parmesan cheese until smooth, cooking for 3-5 minutes.

Add the cooked fettuccine to the skillet, tossing until coated with the sauce. If the sauce is too thick, add reserved pasta water gradually.

Serve immediately, garnished with parsley or green onions, and enjoy with a side salad or garlic bread.