Preheat oven to 325 degrees. Arrange onion, carrot, celery and garlic in a roasting pan.
In a small bowl, combine salt, thyme, rosemary, garlic powder, sage, pepper and cayenne; set aside. Brush turkey breast with olive oil and rub seasoning mixture into all sides.
Place turkey on top of vegetables; bake, uncovered, for 30 to 40 minutes or until cooked through. Serve with vegetables.