Heat oil in a medium skillet, over medium heat. Add the onion slices and sauté until lightly browned.
Lightly grease or spray a casserole dish. Arrange the caramelized onions on the bottom and layer the potato, tomato and squash, edges overlapping, on top. Season with salt and pepper, sprinkle with thyme and Parmesan and drizzle with olive oil.
Cover the dish with foil and bake for 30 minutes. Remove the foil and bake another 20-30 minutes or until the potato is tender.
Notes
Inspired by a September 2011 Wholeliving.com recipeNutrition information is calculated using an ingredient database and should be considered an estimate. When multiple ingredient alternatives are given, the first listed is calculated for nutrition. Garnishes and optional ingredients are not included.