Preheat your grill as hot as it goes. Mine is 600 degrees F and it works great. Make sure your grates are clean.
Prep and portion the ingredients, except for the basil.
Combine the tomatoes, garlic, scallion, capers, 1 tsp salt, 1/2 tsp black pepper, 3 tablespoons EVOO & 1 tablespoon champagne vinegar. Mix gently and set aside. (Do not mix in the basil. Keep the basil set aside.)
Drizzle tuna steak with olive oil
Season the steaks with salt & fresh ground pepper
Rub the sides and add more seasoning if necessary to ensure all sides are coated
When the steak is well seasoned, place it on the hot grill for 1 minute for rare tuna steaks.
Armed with tongs and a good spatula so you are prepared, flip the tuna and cook for 1 minute more.
Remove from grill and let the tuna rest for a minute or two while you finish the salad.
Julienne the basil and and mix it into the tomato & caper mixture.
Slice the tuna across the grain.
Plate the tuna slices and top with the tomato & caper salad.