Wash the aubergines and cut in half vertically.
Heat an abundant dose of oil. When hot fry the aubergines until golden and dry.
With a spoon remove the pulp leaving only a centimetre on the peel. Keep the pulp to one side.
Heat two spoonfuls of oil in a frying pan and brown the onion already chopped. Add the aubergine pulp. Cook for a minute and remove from the heat.
Cool the mixture and add the crumbled tuna fish, the Ragusano in thin slices, the capers and crumbled anchovies. Mix until homogeneous. Add oil, salt and pepper.
Fill the aubergine peels with the mixture. Lay out in an oiled oven dish. Cover with breadcrumbs and bathe with oil.
Bake au gratin in the oven and serve hot.