Cut the eggplant, zucchini, and peppers into batonnet.
Halve the cherry tomatoes and set them aside.
Mix the vegetables, except the tomatoes, together with the onions, garlic, pearl onions, and chopped basil. Spread out on the bottom of a roasting pan and drizzle with olive oil. Mix well until the vegetables are well coated.
Cook gently at 300◦F (150◦C) for 1 hour.
Add the tomatoes then cook for another 10 minutes.