Start by prepping all your veggies. Wash them thoroughly. Slice the tomatoes, zucchini, and potatoes into even pieces for consistent cooking.

In a large skillet, heat a drizzle of good-quality olive oil. Add the thinly sliced onions and cook them on medium heat. You want them to soften and caramelize a bit, which will build flavor.

While the onions are cooking, finely mince your garlic. Add it to the skillet once the onions become translucent. Sauté it for about a minute, just until fragrant.

In a baking dish, layer a mix of your prepared tomatoes, potatoes, and zucchini. Sprinkle salt, pepper, and thyme leaves throughout the layers. Don’t forget to drizzle some olive oil.

Sprinkle the Gruyère cheese over your vegetable layers. This will create a lovely, golden crust as it bakes.

Cover your baking dish with aluminum foil and bake in a preheated oven at 375°F (190°C) for about 30 minutes. Then remove the foil and bake for an additional 15-20 minutes until everything is tender and bubbly.