Put the chickpeas in a pot of water and leave them overnight to soak . The next day, in a saucepan, cook the chickpeas for about 40 minutes. Then strain and spread across a baking pan .
In a saucepan, add the half of a cup of oil and saute the finely chopped onions and garlic. Add the peeled and diced tomatoes. Saute for 2-3 more minutes.
Spread the sauted ingredients across the baking pan with the chickpeas. Add the remaining olive oil , the salt and pepper , the rosemary and the peeled and sliced lemon. Add water to cover the chickpeas. Bake in a preheated oven for 30 minutes at 180° C.