Season the chicken breasts with Cajun seasoning, salt, and pepper. Heat olive oil in a skillet and cook the chicken for 6-7 minutes on each side until golden brown. Remove and let rest before slicing.

In a pot, boil salted water and cook fettuccine according to package instructions until al dente, about 8-10 minutes. Drain and set aside.

In the same skillet, melt butter and sauté garlic for 1 minute. Add heavy cream and bring to a simmer. Stir in Parmesan cheese until melted and smooth. Season with salt and pepper.

Add cooked fettuccine to the Alfredo sauce and toss to coat. Top with sliced chicken and garnish with parsley if desired.