Chop tomatoes and basil, place in a pot with olive oil and onion. Cook on a very low heat for 3 hours.
Peel eggplant and slice lengthways into finger-width strips. Dust the slices lightly in flour. In a wide, flat pan, pour in the olive oil to a depth of 1cm. Heat the oil, avoiding it becoming too hot. Fry the slices of eggplant in batches, laying the cooked eggplant on paper towels.
Coat the base of an ovenproof pan in the tomato sauce. Sprinkle with fresh basil. In a single layer, lay a third of the sliced eggplant over the sauce. Top with some of the mozzarella and parmigiano.
Repeat the layers another 2 times. Finish with a layer of tomato sauce, sprinkle with mozzarella and parmigiano. Bake at 180degC for 12 minutes or until browned on the top.
