In zip lock bag, cover the pork tenderloin with 1/4 cup olive oil and ½ cup balsamic vinegar.  Close top of bag and place in refrigerator for 2 to 24 hours. 30 minutes before cooking, remove from refrigerator and allow to come to room temperature. Preheat broiler or grill; place pork on broiler pan or grill grates and sprinkle sea salt liberally over top. Close oven/grill top and cook directly on heat 2 minutes to sear the outside. Turn pork over, drizzle oil/vinegar mixture over top and sear other side 2 minutes.