If your steak was chewy, a couple of factors could be causing this. It could be the type of steak you are using and how long you cooked it for. Skirt steak can be tougher than flank steak because of the muscle fibers, but it also can be richer in flavor and juicer. If Skirt steak is cooked longer and well done, it will be very tough, chewy, and not enjoyable in a taco or quesadilla. We always salt our steak before we marinate it to ensure we don't have a tough and chewy steak. Salt draws out the moisture in the steak, where it's dissolved, creating a brine that is then re-absorbed back into the steak. The meat's lean muscle proteins are broken down and made juicier and more tender. Always use an instant-read thermometer to ensure doneness. We recommend cooking carne asada to medium at 145°F. Anything hotter will be well done, and the steak could be chewy and tough. When removing the steak from the heat, let it rest for a few minutes and always cut against the grain first before cutting it into chunks.