Make the sauce base

• Heat olive oil in a frying pan and sauté the onion and bell pepper until softened.
• Add the garlic and cook until fragrant.
• Stir in the tomato paste, crushed tomatoes, thyme, salt and pepper, then simmer until thickened.

Slice the vegetables

• Slice the eggplant, zucchini, yellow squash and tomatoes into thin, even rounds.

Assemble the dish

• Spread the sauce base evenly in the baking dish.
• Arrange the vegetable slices in alternating, overlapping layers over the sauce.

Bake

• Drizzle with olive oil and season with salt and pepper.
• Bake until the vegetables are tender and lightly browned.

Serve

• Let the ratatouille rest briefly, then serve warm.