Heat 4 tablespoons oil in a 12-inch nonstick skillet over medium heat. Add eggplant and cook, stirring occasionally, until lightly browned and soft, 5 to 10 minutes. Transfer to a plate.Advertisement
Heat the remaining 2 tablespoons oil in the pan. Add onion and cook, stirring frequently, until soft and lightly golden, 6 to 8 minutes. Stir in garlic and cook, stirring, for 30 seconds. (If the pan seems too dry, push the onion and garlic to the side, add a drizzle of oil, then continue cooking.)
Stir in celery; cook, stirring frequently, until softened and slightly golden, 5 to 7 minutes. Stir in tomatoes; cook, stirring, about 2 minutes. Return the eggplant to the pan; stir until well combined. Sprinkle sugar over the eggplant mixture (omit if using Chinese eggplant, which is naturally sweeter), stir to combine and cook for about 30 seconds. Stir in vinegar, salt and pepper. Taste and add 1 to 2 tablespoons vinegar, if desired. Stir in olives and capers; cook for 1 minute. Remove the pan from the heat. Stir in basil and pine nuts.
Make Ahead Tip: Cover and refrigerate for up to 3 days.
Tips: If you're using large, common globe eggplant, which can be more bitter than other varieties, salting beforehand can reduce bitterness. To salt: Place prepped eggplant in a large colander over a bowl and mix with 1 tablespoon salt. Top the eggplant with a plate weighted down with cans. Let sit for 30 minutes to 1 hour before using. Rinse well with cold water, then dry with paper towels.
Toast chopped, small or sliced nuts in a small dry skillet over medium-low heat, stirring constantly, until fragrant and lightly browned, 2 to 4 minutes.
2 vegetable, 5 fat