Heat oven to 450°F. Place tomato slices on paper towels. Sprinkle with 1/2 teaspoon of the salt and let stand for 15 minutes. Pat dry with paper towels.
Coat a 2-quart oval baking dish with 1 teaspoon of the olive oil. Sprinkle 1 tablespoon of the bread crumbs over the bottom of baking dish.
Place half of the tomato slices in prepared baking dish, overlapping as necessary. Season with 1/8 teaspoon of the salt and 1/4 teaspoon of the black pepper. Sprinkle 1 teaspoon of the olive oil, 1 tablespoon of the oregano and 1 teaspoon of the thyme over the top. Tuck in the sliced garlic and sprinkle the remaining 2 tablespoons of bread crumbs over the top. Place remaining tomato slices in dish and season with remaining 1/8 teaspoon salt and 1/4 teaspoon pepper. Sprinkle remaining oil, oregano and thyme over the tomatoes.
Bake at 450°F for 30 minutes. Scatter Parmesan on top; bake an additional 10 minutes.
Remove gratin from oven and let stand for 10 minutes before serving.