Slice onion thinly and saute in olive oil, until more than soft, almost caramelized. Set aside. Slice potatoes, tomatoes, zucchini the same size. Layer starting with zucchini,onion, potato, tomato, herbs. In between each layer, drizzle olive oil, sprinkle with herbs and parmesan cheese (the good kind). Keep the dish shallow. Each layer of potato and tomato is not a full layer, touching or over lapping, more scattered.