Wash and chop eggplant and potatoes into equal-sized cubes.
Heat oil in a large pan over medium heat.
Add cumin seeds and let them crackle.
Add chopped onion and cook until soft and light golden.
Add tomatoes, turmeric, coriander powder, red chili powder, and salt. Cook until mixture thickens and releases oil.
Add diced potatoes and cook for 3–4 minutes.
Add eggplant and mix gently.
Add ¼ cup water. Cover and cook on low heat for 15–20 minutes, stirring gently.
Once vegetables are tender, sprinkle garam masala.
Garnish with fresh cilantro and serve with lemon juice if desired.