1. In a small bowl, combine garlic powder, pepper, and salt. In another small bowl, combine half of the garlic powder mixture, the tomatoes, 1 tablespoon of the oil, the oregano, thyme, and vinegar. Set aside.
2. Brush eggplant slices with the remaining 1 tablespoon oil and sprinkle with the remaining garlic powder mixture.
3. For a charcoal grill, grill eggplant slices on the rack of an uncovered grill directly over medium coals for 6 to 8 minutes or just until tender and golden brown, turning once halfway through grilling and topping with the cheese slices for the last 2 minutes of grilling. (For a gas grill, preheat grill. Reduce heat to medium. Place eggplant slices on grill rack over heat. Cover and grill as above, topping with cheese as directed.)
4. Place eggplant slices on top of toasted bread slices. Top with tomato mixture