Note: Sweet and sour eggplant relish can be made ahead and stored in a sealed container in the refrigerator for up to 1 week.
- 1 small eggplant, cut into 1/2-inch dice (about 1 quart)
- Kosher salt
- 6 tablespoons extra-virgin olive oil
- 1 medium onion, finely diced (about 1 cup)
- 2 stalks celery, finely diced (about 1/2 cup)
- 2 tablespoons tomato paste
- 3 tablespoons capers, rinsed, drained, and roughly chopped
- 1/4 cup golden raisins
- 2 tablespoons sugar
- 3 tablespoons red wine or balsamic vinegar
- 1 cup canned whole peeled tomatoes with their juice, chopped into 1/4-inch pieces
- Freshly ground black pepper
- 3 bunches (about 2 1/2 pounds) broccoli rabe, thick stems trimmed, cut into 3-inch lengths
Place eggplant on a large plate lined with a triple layer of paper towels or a clean kitchen towel. Season with salt. Top with another triple layer of paper towels or a clean kitchen towel. Top with another large plate. Microwave on high power until eggplant has lost most of its moisture and appears slightly shriveled, about 8 minutes.
Meanwhile, heat olive oil in a medium saucepan over medium-high heat until shimmering. Add onion and celery and cook, stirring frequently, until softened and translucent, about 8 minutes. Add eggplant and cook, stirring occasionally, until eggplant is starting to break down, about 5 minutes longer. Add tomato paste, capers, raisins, sugar, vinegar, and chopped tomatoes and stir to combine. Bring to a gently simmer and cook, stirring occasionally, until reduced into a thick, stew-like consistency, about 20 minutes. Season to taste with salt and pepper. Set aside.
Bring a large pot of salted water to a boil. Add broccoli rabe and cook until tender, about 6 minutes. Drain in a colander and transfer to a large bowl. Add eggplant mixture and toss to combine. Season to taste with salt, pepper, and more vinegar or sugar as desired. Serve.