Caponata, a classic Sicilian mix of cooked veggies tossed with vinegar, is tasty at room temp. Arrive early and you'll be the Greatest BBQ Guest Ever.
Arrange racks in the top and bottom thirds of the oven; preheat to 400°. In a colander, toss the eggplant and 1 tbsp. salt. Let stand for 30 minutes.
Line 2 rimmed baking sheets with parchment paper. Rinse the eggplant briefly; press dry with paper towels. In a large bowl, season the eggplant with salt and pepper. Add 2 tbsp. oil; toss until coated. Spread out on 1 baking sheet. In the same bowl, toss the remaining 3 tbsp. oil, the onion, tomatoes, and bell pepper; season. Spread out on the second baking sheet. Roast, rotating the sheets and stirring once halfway through roasting, until the vegetables are tender and charred in spots, about 40 minutes. Let cool.
In a medium bowl, whisk the vinegar and sugar until the sugar dissolves. Mix in the vegetables with any juices. Add the olives, capers, and chopped basil; season. Garnish with small basil leaves. Serve with crackers.