This gets asked here a lot (because it's a great question) -- here's some info from our FAQ.

Mediterranean Peasant fare ALWAYS consisted of dry Brown bread. Especially Barley but Wheat was more prized. You can still purchase this bread in specialty Greek and Levantine shops in US Cities. "Paximadia"The bread is HARD but thats not how its eaten. Its slightly moistened, and then olive oil and salt. It tastes awesome when you do that. This was the base, and then whatever else could be added. Fish, cooked Vegetables, cheese, meat stew, charcutterie preserved meat.Olive Oil is a hugely important source of fat calories and every meal had it. Cheese was a hugely important protein source.

(South Italy was heavily Greek in Roman and Byzantine period thru medieval era, so they ate similarly and had the same crops geography) People in very traditional and religious Greek cultures eat similarly to premodern era when its Fasting season before Christmas and Easter; no meat, no dairy, so staples are bread ; vegetable stews with lots of oil. Greek vegetable stews are mushy and full of oil and very heavy, and do have a lot of tomato today, I just imagine it without. The way Mediterranean Spring stews have no tomatoes, they have artichokes, celery, carrots.
Its important to realize: Tomatoes are a summer vegetable along with cucumbers, are not eaten the rest of the year. Modern era theres canned tomato pastes to make stews and sauces year round but that's a very recent addition. The Italian American Red Sauce joint that has the same menu 365 days a year is a very American Tradition; base a whole cuisine on non fresh items...Basically, Large cans of tomato paste. This has no equivalence on the other side of Atlantic outside of fast food chains.
Its very important to note seasonality, which is STILL the basis for eating everywhere except USA that expects bad tomatoes in winter from South America. The modern mediteranean does NOT eat Tomatoes when not in season, they taste like shit.