Preheat oven to 190degC.
Coat a dish, approximately 20x30cm, with 1 tbsp oil, and rub with cut garlic.
Slice potatoes and zucchini into 2-3mm round slices.
Slice tomatoes into 4-5mm slices
Arrange potatoes, zucchini, and tomatoes in overlapping layers in the dish
Season with salt and pepper.
Drizzle with remaining 2 tablespoons oil, and sprinkle with thyme.
Add grated cheese, if using.
Cover with foil and bake until potatoes are tender, 35 to 45 minutes.
Remove foil and continue baking until top is golden brown, about another 25 minutes.
Remove from oven and serve.