This delicious appetizer goes well on crackers or bread. It has just enough zip to be interesting but isn't spicy.
Place the eggplant cubes into a colander set over a bowl and salt them well. (I use about 2 teaspoons of salt. Don’t be concerned about eating all this salt; you’ll rinse this salt off – it helps drain the water out of the eggplant.) Toss the cubes and salt with your hands. Set aside.
Go back to the eggplant and run the cubes (in the colander) under cold water, tossing them with your hands and pressing them until you have thoroughly rinsed the salt out. Press the cubes again, to drain out as much water as possible.
For the eggplant, celery, and onion, don’t stress over total uniformity as you chop, but try to get the pieces as small as possible. Keep in mind that spreading caponata on a cracker is not easy if the pieces are too big. The pieces will diminish in size slightly, but not much during preparation and they remain distinct. The easiest and most efficient way to cut these vegetables is to make slice, then chop, holding several slices together.