Preheat oven to 400 degrees. Lightly oil a 2-quart baking dish. In a bowl, combine 1 1/2 cups fresh plain breadcrumbs, 1/3 cup grated Parmesan, 1 tablespoon finely grated lemon zest, leaves from a few sprigs fresh thyme and 2 tablespoons extra-virgin olive oil; season with coarse
salt and ground pepper.
Arrange 4 large tomatoes cut into 1/2-inch slices, in prepared baking dish, overlapping slightly; season with salt and pepper. Top with breadcrumb mixture. Bake until tomatoes are tender and crumbs are golden brown, 15 to 20 minutes.