Unpack pork tenderloin and pat dry with paper towel. Place in stainless steel bowl (or other safe cooking surface). Salt generously. Let sit for 1 hour. If you don't have an hour to wait, just salt right before cooking.
After the hour, preheat oven to 350. Heat your carbon steel or cast iron pan to medium high heat, add coconut oil. In another bowl create your cornstarch dredge, add sumac and cayenne to cornstarch, mix evenly.
Season pork tenderloin with fresh ground pepper. Then, generously coat tenderloins with cornstarch mixture. Let rest for 10 minutes. If you are short on time you can skip this step, however, it may not turn out as crispy on the outside.
Pan should be almost smoking at this point, that means it's ready, add cornstarch coated tenderloin to pan, brown on all sides. Once browned, place in oven until it reaches an internal temperature of 145 degrees.
Let rest for 5-10 minutes before serving.