Whisk together the rum, salt, pepper, cinnamon, powder, oregano, sage, vinegar, and lemon juice in a bowl; pour into a gallon-sized, resealable plastic bag. Add the onion and steaks to the marinade. Seal the bag, squeezing out as much air as possible. Allow to marinate in refrigerator 2 1/2 hours.
Heat the olive oil in a large skillet over medium heat. Cook the steaks with the skillet covered to desired doneness, about 3 minutes per side for medium rare.
