Preheat the oven to 400 degrees. Line a large, rimmed baking sheet with parchment paper to prevent the eggplant from sticking to it.
Place the cubed eggplant in a colander and lightly sprinkle with salt. Allow to drain for 20 minutes while you prep the remaining ingredients.
On a large baking sheet, toss the diced eggplant with 3 tablespoons of olive oil and sprinkle with pepper. Do not salt. Roast in the oven for 20-25 minutes or until eggplant is tender and lightly browned.
While the eggplant is roasting, heat the remaining oil in a large skillet over medium heat. Add the diced onion, celery, and red pepper. Sauté until soft, about 5 to 7 minutes. Add canned tomatoes and cook an additional 5 minutes until thickened.
Add the sugar, vinegar, pine nuts, olive, raisins, and capers to the skillet. Bring the mixture to a boil, then reduce heat and let it simmer for about 10-15 minutes or until the mixture thickens.
Stir in the roasted eggplant. Cook for another 5 to 10 minutes, stirring occasionally. Season to taste with salt and black pepper. Add a pinch of red pepper flakes if you like.
Remove from heat and let it cool for 30 minutes. Sprinkle with fresh herbs and serve warm or at room temperature with crostini.
Notes
All Stovetop Instructions: Heat 3 tablespoons of oil to a large skillet. Add the eggplant and cook over medium heat, stirring frequently. Once browned, about 10 minutes. Push to the side. Add the remaining oil and the onion, celery, and pepper. Proceed with the recipe.