While the eggplant is baking, add 2 tablespoons of oil in a dutch oven or heavy pot over medium heat. Then add cumin seeds.
Once the cumin seeds begin to splutter, add onions and saute for 10 minutes or until the onions turn golden brown.
Add the garlic, ginger, Serrano pepper and spices. Stir-fry for a minute, add tomatoes and mix well.
Cover the pan with a lid and cook for 10 minutes.
Remove lid and stir-fry for another 5 minutes.
Stir in the cooked eggplant and cook for another 5 minutes.
Garnish with cilantro and serve.