Roast the vegetables: Preheat oven to 425°F (220°C). In a large bowl, toss eggplant and bell pepper with 2 tablespoons olive oil, salt, and pepper. Trim the top ¼ inch from the garlic head, place it in the same bowl and turn to coat lightly with the residual oil, then wrap loosely in foil. Arrange everything on a large rimmed baking sheet and roast 25–30 minutes, until eggplant is deeply browned and pepper is soft and lightly charred.
Prepare the roasted aromatics: Cool slightly. Peel the bell pepper and roughly chop the flesh. Squeeze the softened garlic cloves into a small bowl and mash to a paste.
Bloom the spices: In a Dutch oven or large pot, heat the remaining 1 tablespoon olive oil over medium heat. Add cumin, smoked paprika, and coriander; toast 30–45 seconds until highly fragrant. Immediately add the tomatoes with their juices.
Simmer and meld: Bring to a simmer. Stir in the roasted eggplant, chopped bell pepper, and mashed garlic. Reduce heat to low, cover, and simmer gently for 15 minutes, stirring occasionally.
Finish and mash: Off the heat, stir in lemon juice, sumac, cilantro, and parsley. Mash with a potato masher to a rustic, chunky-smooth consistency.
Serve: Transfer to a serving bowl. Drizzle with extra-virgin olive oil (optional) and garnish with cilantro. Serve warm or at room temperature with whole-wheat pita, fresh vegetables, or alongside grilled fish.