Preheat the oven to 475°F with a rack in the upper third.

Line a large sheet pan with parchment paper or foil for easier cleanup.

Put the eggplant, cherry tomatoes, and onion on the sheet pan.

Drizzle the vegetables with 2 tablespoons of the olive oil. Sprinkle on the cumin, 1/2 teaspoon of the salt, and the black pepper, then toss and spread everything into one layer.

Roast the vegetables for 25 minutes, stirring once halfway through, until the eggplant is soft and browned at the edges and the tomatoes have burst.

While the vegetables roast, drain and rinse the chickpeas in a colander. Set them aside.

Juice half of the lemon and keep the other half cut into wedges for serving.

Heat the remaining 1 tablespoon olive oil in a large soup pot over medium heat.

Add the garlic to the pot and cook for 30 to 60 seconds, stirring, until it smells fragrant. Do not let it turn dark brown.

Scrape the roasted eggplant, tomatoes, onion, and all the juices from the sheet pan into the pot.

Add the chickpeas, vegetable broth, and the remaining 1/2 teaspoon salt to the pot. Raise the heat to high and bring the soup to a boil.

Lower the heat to medium-low and simmer for 10 minutes so the roasted vegetables flavor the broth.