1. Rinse the tuna steaks under cold water and pat dry. Brush them with 1 teaspoon olive oil and season with salt and pepper.
2. Preheat grill or broiler. Meanwhile, mix the remaining ingredients in a small bowl and set aside.
3. Grill or broil the steaks on high heat, about 2-3 minutes per side or until desired doneness.
4. Top the tuna steaks with the tomato-olive mixture.