Preheat the oven to 375°F/190°C.
In an oven-proof skillet, over the stovetop on medium-high heat. Heat olive oil, and saute the onion and carrot until the onions are soft and translucent.
Add garlic, and cook for 30 seconds.
Add tomato sauce, water, and thyme. Stir and cook for 1 minute then remove from heat. Taste the sauce, and adjust the seasonings if desired (salt and pepper).
Add the sliced tomato, zucchini, and potatoes to the dish. With a rubber spatula stir to cover the vegetables with the sauce.
Cover with an oven-proof lid or foil, and bake in the oven for 30 minutes covered.
Uncover, and cook for 5 more minutes then check for doneness (the potatoes should be easily pierced with a fork, if not then cook for 5 more minutes and check again).
Add the cheese, and place under the broiler for 3-5 minutes or until the cheese has melted and the top is lightly browned.