Adapted from License to Grill by Chris Schlesinger and John Willoughby. Make sure you get steaks that are really thick, so they can get a good, strong sear on the outside and still be rare at the center.
In a small bowl, combine the rosemary, garlic, salt, and pepper and mix well. Rub the steaks all over with this herb mixture and grill them over a hot fire for 5 to 7 minutes per side for medium-rare. To check for doneness: Cut into one of the steaks to see that it is about one degree less done in the center than you want, since it will cook a little more after you take it off the fire. When the steaks are done to your liking, take them off the grill and let them rest for about 3 minutes.
Meanwhile, make the relish:
Rub the eggplant and onions with the oil, sprinkle with salt and pepper to taste, and grill around the edge of the fire, just barely over the flame (you want a medium-hot fire for these vegetables), until they are well browned and soft throughout, 3 to 4 minutes per side. Pull them off the grill, dice them into bite size chunks, and place them in a medium bowl. Add the garlic, vinegar, olive oil, parsley, and salt and pepper to taste and toss well.
By this time the steaks should be just right, serve them up with a few heaping spoonfuls of the relish. Enjoy!