Peel the onions and wash them along with the rest of the vegetables. Place all the vegetables directly on a baking sheet in a preheated oven at 400°F (200°C). Drizzle with olive oil and sprinkle with salt. Roast for 1 hour.

Peel and chop the tomatoes, making sure to keep all their juices. Peel and chop the eggplants, and chop the onions as well.

In a large glass dish, arrange all the vegetables and pour over the reserved juices. Peel and finely chop the garlic cloves, then sprinkle them over the vegetables. Add more olive oil and salt to taste.