Preheat oven at 400F/200C
1. Using a Mandolin, thinly slice the rutabaga, sweet potato, zucchini, and potatoes.
2. Quick sauté in Extra Virgin Olive Oil the Onions, garlic, tomatoes, season with salt and pepper a pinch of the herbs de Provence, fresh thyme and the sprig of rosemary.
3. Place this tomato sauté in a gratin-stone ware or glass baking dish will work to.
4. Start layering the root slices, over the sautéed tomato-onion-garlic. Alternate the colors and different type of roots and zucchini (see photo below) and work all your way around.
5. Brush the top with the melted butter and herbs and sprinkle with the grated Parmesan cheese.
6. Bake for about 25-30 minutes, cover with foil for the first 15 minutes of baking, and remove for the last 10-15 minutes to achieve a great gratin crust until golden brown.
7. Serve warm.