Wash, pat dry and prick eggplants. Roast them over open flame or in a tandoor/preheated oven until the skin scorches and starts peeling off and eggplants start to shrink. Let them cool.
You can cool them by dipping them in water. Remove skin and mash the pulp completely. Heat oil in a kadai. Add cumin seeds. Cook for half a minute and add onions and sauté until translucent.
Add ginger and green chillies and cook for a minute. Add red chilli powder and mashed roasted eggplants. Cook for seven to eight minutes over medium heat, stirring continuously.
Add salt to taste. Add tomatoes and cook on medium heat for seven to eight minutes or till oil separates.
Garnish with chopped coriander leaves and serve hot.