To prepare the caponata, sauté eggplant and bell peppers, separately, for 3 minutes in olive oil. Save to the side. Cook onions in sauce pot with a drop olive oil. Add tomatoes and cook 3 minutes; then add olives. Add celery and capers. Cook for 3 minutes, and add the sautéed peppers and eggplant. Remove from heat, cool and add sea salt, pepper and vinegar.
To prepare the socca, sift the chickpea flour into a large mixing bowl and add the salt, pepper and baking powder. Gradually pour in the water, whisking constantly to avoid lumps. Slowly stir in half of the olive oil. Mix until dough has formed. Cover, and save overnight.
Preheat oven to 450ºF (230ºC). Heat a pizza dish, spray with olive oil and pour in batter. Spread out thinly, and bake for 10 minutes. Remove from oven and brush olive oil on top and place under the broiler to crisp up. Slice and serve with the caponata.