Drape tomato slices over colander, sprinkle with salt, and let drain 45 minutes.

Spread zucchini on baking sheet, and sprinkle with salt. Let stand 30 minutes to sweat out excess moisture. Rinse well, and pat dry.

Preheat oven to 375 degrees F. Heat 1 teaspoon oil in nonstick skillet over medium-high heat. Saute zucchini 3 to 4 minutes, or until golden. Transfer to plate. Do this in 2 batches if necessary, adding more oil between batches.

Layer half of zucchini slices in 8-inch-square baking pan. Top with half of tomatoes. Sprinkle with half of garlic, 1 tablespoon olives, half of basil, and 1/4 cup Parmesan cheese; season with freshly ground black pepper. Repeat with remaining zucchini, tomatoes, garlic, olives, and basil. Drizzle top with 1 tablespoon oil, and sprinkle with remaining 1/2 cup cheese. Cover with foil, and bake 10 minutes. Remove foil, and bake 20 minutes more, or until cheese is melted and gratin is bubbling. Let stand 5 minutes before serving.