A tonneau cover assembly with a top cover connected to a cable tensioning system that eliminates the need for side rails to both locate and tension the top cover. The cable tension system seals out environmental elements and holds the tonneau cover and fabric management bows of the assembly in place. The assembly includes a front attachment assembly and rear attachment assembly connected to cables, where the front attachment provides a forward mounting location and seals a front bow to the vehicle. The rear attachment assembly holds the top cover in a closed tensioned state until the cover is opened by an operator. The tonneau cover assembly reduces weight and complexity, while eliminating the need for side rails.