In a bowl, rub the chicken with 1 tablespoon of the Cajun seasoning and marinate for about 10 to 15 minutes.
Grill over hot coals or in a grill pan for about 5 to 7 minutes on each side or until thermometer inserted in the center reads 165 F. Remove from heat and let stand for a few minutes before slicing. Keep warm.
In a large saucepan or Dutch oven over medium heat, add olive oil. While still warm, add garlic and cook for about 1 to 2 minutes or until aromatic. Add the remaining 1 tablespoon Cajun seasoning and cook, stirring regularly, for about 30 to 40 seconds minute.
Add marinara sauce and chicken broth, and bring to a simmer. Season with salt and pepper to taste. Continue to cook for about 10 to 15 minutes until the sauce is slightly reduced and thickened.
Meanwhile, in a pot over medium heat, bring about 4 quarts of lightly salted water to a boil. Add angel hair pasta and stir gently. Cook in the boiling water, uncovered, for about 3 to 4 minutes or until firm to bite. Drain well.
To serve, divide pasta on serving plates. Spoon sauce and place sliced chicken on top. Garnish with Parmesan cheese, if desired.