Arrange tomatoes on a serving platter. Heat a cast-iron grill over high heat until very hot. Quickly sear tuna on each side for 1 minute per side. Remove from heat. Mix the garlic, olive oil, vinegar, red pepper flakes, and olives in a bowl and set aside. Thinly slice tuna. Add to bowl with olive oil mixture and toss until well coated. Spoon over tomatoes, sprinkle lightly with salt, and serve.
Recipe courtesy of Juan-Carlos Cruz