2 pounds of eggplant (4 small Italian eggplants or 2 medium globe eggplants) washed and cut into 3/4-inch cubes (skin on)
2 tablespoons kosher salt
3/4 cup good quality olive oil, divided
1 large red onion, halved and thinly sliced
4–5 tender inner stalks of celery, roughly chopped (about 1 cup chopped)
3 large garlic cloves, minced
2 red bell peppers seeds and ribs removed, cut lengthwise into thin strips
3 tablespoons tomato paste
4 ounces pitted green olives, coarsely chopped (about a cup chopped)
1/3 cup yellow raisins
1/4 cup capers, drained
6 tablespoons red wine vinegar
3 tablespoons granulated sugar
Kosher salt, to taste
Salt & Rinse Eggplant: Line a jellyroll pan with paper towels. Spread out eggplant cubes and sprinkle with 2 tablespoons salt. Cover with paper towels. Pace another baking tray on top and add a weight, such as heavy skillet. Let that all stand for 1/2 hour to an hour. (you can cut up the other veggies while you wait) Rinse the eggplant in a mesh colander. Line the same jellyroll pan with more paper towels. Transfer the rinsed eggplant to the tray and pat it dry with another layer of paper towels.
Saute the Eggplant: Heat 1/4 cup oil in a large skillet (cast iron is best) over medium heat until hot but not smoking. Add half the eggplant in a single layer. Leave it undisturbed for two minutes so it browns a bit. Continue to cook, stirring often, for another 5 minutes, until eggplant is brown in spots and starting to soften. Transfer to a paper-towel-lined mesh colander. Add another 1/4 cup olive oil to the skillet and repeat with the rest of the eggplant.
Add another 1/4 cup olive oil to the skillet. Add the onions, garlic and celery. Cook, stirring occasionally, for 5 minutes, until the onions are softened. Add the bell peppers and cook for 5 minutes, stirring occasionally, until the peppers are softened. Add the tomato paste, olives, raisins capers, and 3 tablespoons water. Cook, stirring frequently, for 8 minutes. Add the eggplant to the skillet. Whisk the sugar and vinegar together in a small bowl and pour into the skillet. Lower the heat to medium-low and simmer the mixture for 15 minutes, stirring occasionally. Season with salt, to taste. Serve warm or at room temperature. Caponata will keep for a week covered in the fridge and is best served at room temp after a day of letting the flavors meld.