Peel and chop three of the four onions. Peel the fourth onion but leave it whole.

Cut the eggplant into thin (1/3 inch, 1 cm) slices, cut them lightly with a sharp knife and sprinkle them with fine salt and allow the pieces to "sweat" for about 20 minutes to drain the bitter juices. Once the eggplant begins to sweat, rinse off the salt and pat dry before frying.

Score the tomato skin, dip them in boiling water for 30 seconds to 1 minute and peel.

Remove the seeds from the peppers and cut them into thin strips.

Cut the courgettes into medium slices.

Peel the garlic and cut it into thin slices.

In a large cast-iron casserole dish, fry the onion in olive oil seasoned with a little anchovy puree or pissalat. Add a sprig of thyme and freshly ground pepper.

Stir with a wooden spoon. Before the onion starts to brown, add the crushed tomato pulp, bay leaf, parsley, saffron, cloves stuck in an onion, and sugar to remove the acidity of the tomato.

In one or more frying pans, fry the eggplant (10 minutes), the peppers (10 minutes), and the courgettes (5 minutes). Season with salt and pepper and remove the excess oil by draining the vegetables on a paper towel before placing them in the tomato sauce in the casserole dish.

Cover the mixture with baking paper (foil or parchment) and seal the pot with the lid. Simmer for 40 to 45 minutes, preferably in the oven at 150°(300° F)/180° C (350° F).

Adjust the seasoning at the end of the cooking time. You can add pitted olives just before serving with a little fresh basil.

You can omit the cloves.

You can also simply finish cooking on low heat in the closed casserole. Some old Niçois used to fry a nice piece of blanched small salt codfish at the same time as the onion for 10 minutes to have a complete summer dish.