Preheat oven to 450 degrees F. Spray a square 8-inch baking dish with oil. Place the chicken breasts on a cutting board.
In a small bowl, use a fork to mix the Cajun seasoning ingredients.
Rub the cajun seasoning into the chicken breasts on both sides.
Place the coated chicken pieces in the greased baking dish. Spray their tops with oil. Be generous with the oil - it protects the chicken from drying out and it also protects the herbs from burning in the hot oven.
Bake until cooked to an internal temperature of 165 degrees F, about 20 minutes.
Place on a plate, cover loosely with foil and allow to rest 5 minutes before serving.