Preheat the oven to 375°F (190°C).
In a 10-inch square baking dish, mix tomato paste, onion, garlic, water, and 1 tbsp olive oil. Season with salt and pepper.
Arrange overlapping slices of eggplant, zucchini, squash, and peppers in the dish, forming a colorful spiral.
Drizzle the remaining 3 tbsp olive oil over the veggies. Season with salt, pepper, and thyme. Cover with parchment paper.
Bake for 45 minutes, or until the vegetables are tender and roasted.
Remove from the oven, garnish with basil, and serve warm.