Wash all vegetables for filling.
Remove the stalk and seeds from the peppers. Spoon the tomato pulp with a spoon - don't throw it away, we will use it in the sauce.
Zucchini and eggplant are cut into pieces about 2-3 cm thick and hollow in the middle, leaving a little at the bottom for the base.
Grease with a little oil a deeper baking tray (I used one about 40x20) and arrange the vegetables as close as possible - if it is not filled and you still have the filling you can add more vegetables than in the recipe.