Mix tapenade and rosemary in small bowl. Season steaks generously with salt and cracked black pepper.
Divide olive oil between 2 heavy medium ovenproof skillets set over high heat. Add 1 steak to each skillet and cook until both are browned, about 3 minutes per side.
Spread half of tapenade mixture atop each steak.
Transfer skillets with steaks to oven. Cook both steaks until a thermometer inserted into center of steaks registers 125°F for medium-rare, about 20 minutes. Transfer both steaks to platter.
Pour 2 tablespoons balsamic vinegar into each skillet and cook over medium heat until liquid is slightly reduced, scraping up browned bits, about 1 minute.
Drizzle hot skillet juices over each steak and serve.