Preheat your oven to 375°F. In a bowl, toss the diced eggplant with 3 tablespoons of the olive oil and the salt until every piece is well coated. Spread the eggplant in a single layer on a large, lipped baking sheet. Roast for about 25 minutes, or until it's a beautiful golden brown and a bit soft. Give it a stir halfway through.
While the eggplant roasts, set a very large saucepan over medium heat and add the remaining 3 tablespoons of olive oil. Add the onion, bell pepper, and celery, and cook for about 5 minutes, stirring occasionally, until they’re nice and soft.
Stir in the tomatoes, raisins, olives, capers, honey, white wine, red wine vinegar, and red pepper flakes. Bring the mixture to a bubble, then reduce the heat to low. Continue to cook, stirring often, for about 10 minutes until the vegetables begin to break down into a rustic, sauce-like consistency.
Stir the roasted eggplant pieces into the saucepan. Simmer slowly for about 3 minutes, stirring frequently to prevent scorching, until the caponata is quite thick.
Turn off the heat and let the pan rest for a minute or two. Transfer the caponata to jars or containers, leaving a little space at the top. Let it cool at room temperature for up to 30 minutes, then refrigerate or freeze. It only gets better as the flavors meld.