2 1 1/2 pounds flank steaks |
kosher salt |
2 teaspoons (packed) light brown sugar |
1 teaspoon paprika |
1/4 teaspoon cayenne pepper |
1/4 teaspoon freshly ground black pepper |
vegetable oil (for brushing) |
1 cup finely chopped red onion |
3 tablespoons sherry vinegar, divided |
2 pound cherry or grape tomatoes, halved |
1 cup chopped celery hearts (inner stalks and leaves; from 1 bunch) |
1/2 cup chopped brined green olives plus 2 tablespoons olive brine |
2 tablespoons prepared horseradish |
1 tablespoon worcestershire sauce |
1 teaspoon hot pepper sauce |
1/2 teaspoon celery seeds |
1/4 cup extra-virgin olive oil |
kosher salt and freshly ground black pepper |