Preheat oven to 400 degrees.

Spray a ceramic tart pan or pie dish with nonstick cooking spray.

Spread the tomato paste in the bottom of the baking dish. Sprinkle with salt, pepper, and garlic powder.

Slice tomatoes and zucchini into rounds about the same size in diameter and thickness (about 1/3 inch thick). Starting from the outside, shingle the vegetables until the pan is filled. Sprinkle the top with salt, oregano, and basil. Using a zig-zag motion, sprinkle the vegetables with olive oil. Bake in the oven, uncovered, until edges begin to brown and you can see the tomato paste bubbling up. If using cheese, sprinkle cheese over the vegetables in the last few minutes of cooking, just to melt the cheese.

Serve hot or at room temperature (not recommended to serve at room temp if using cheese).