Wash the tomatoes and cut them crosswise just below the stem. Scoop out the flesh, crush it, and place it with the juice and seeds in a baking dish. Add the tomato coulis, salt, and pepper.
Wash the bell peppers, cut them similarly, or halve them if large, and remove the seeds.
Wash the zucchinis, cut off the tops, and scoop out the flesh with a melon baller. Finely chop the flesh. Remove the stems from the mushrooms and wash the caps.
Wash the baby gem lettuces and chop them. Strip the leaves from the parsley and chop it. Finely chop the chili and the peeled onion. Sauté the onion, zucchini flesh, and chili in a skillet with 10 cl of oil for 10 minutes. Season with salt and pepper. Add the chopped lettuces and parsley, and cook for an additional 5 minutes.
Beat the eggs with the Parmesan in a bowl, seasoning with salt and pepper. Add the sautéed vegetables and mix well. Stuff the vegetables with this mixture.
Preheat the oven to 180°C (356°F). Place the stuffed vegetables on the tomato coulis in the baking dish. Drizzle with the remaining oil and bake for 30 to 35 minutes.