PreparationFor steak: Place steaks on a large rimmed baking sheet; season with salt. Mix sugar and next 3 ingredients in a small bowl; rub all over steaks. Cover; refrigerate 1-3 hours. Let steaks stand at room temperature for 1 hour. Build a medium-hot fire in a charcoal grill, or heat a gas grill to high. Brush grates with oil. Grill to desired doneness, about 5-7 minutes per side for medium-rare. Let rest for 10 minutes. DO AHEAD: Can be made 1 day ahead. Let cool; cover and chill. Bring to room temperature before slicing. For salad: Mix onion and 1 tablespoon vinegar in a large bowl. Let macerate 10 minutes, tossing often. Add tomatoes, celery, and olives. Whisk remaining 2 tablespoon vinegar, olive brine, horseradish, and next 3 ingredients in a medium bowl. Slowly whisk in oil. Add to bowl with tomato mixture; toss to coat. Season with salt and pepper. DO AHEAD: Can be made 4 hours ahead. Cover; chill. Cut steak crosswise into 1/4"-thick slices. Serve salad with steak.
PreparationFor steak: Place steaks on a large rimmed baking sheet; season with salt. Mix sugar and next 3 ingredients in a small bowl; rub all over steaks. Cover; refrigerate 1-3 hours. Let steaks stand at room temperature for 1 hour. Build a medium-hot fire in a charcoal grill, or heat a gas grill to high. Brush grates with oil. Grill to desired doneness, about 5-7 minutes per side for medium-rare. Let rest for 10 minutes. DO AHEAD: Can be made 1 day ahead. Let cool; cover and chill. Bring to room temperature before slicing. For salad: Mix onion and 1 tablespoon vinegar in a large bowl. Let macerate 10 minutes, tossing often. Add tomatoes, celery, and olives. Whisk remaining 2 tablespoon vinegar, olive brine, horseradish, and next 3 ingredients in a medium bowl. Slowly whisk in oil. Add to bowl with tomato mixture; toss to coat. Season with salt and pepper. DO AHEAD: Can be made 4 hours ahead. Cover; chill. Cut steak crosswise into 1/4"-thick slices. Serve salad with steak.