Rub the whole eggplant with a little oil, place it directly over an open flame or under a broiler, and roast, turning every few minutes, until the skin is blackened and blistered on all sides and the flesh feels completely soft.

Transfer the charred eggplant to a covered bowl or plate and let it sit undisturbed so the trapped steam loosens the skin and makes peeling easier.

Peel off the charred skin under running water, discard the green stem, and mash the smoky flesh with a fork into a coarse pulp.

Heat the mustard oil in a kadai until it shimmers, then add the cumin seeds and let them sizzle and turn fragrant.

Add the finely chopped onions and sauté, stirring frequently, until they turn golden brown and softened.

Stir in the chopped ginger, garlic, and green chili, and sauté until the raw smell disappears.

Add the chopped tomatoes and cook, mashing them occasionally with the spatula, until they turn soft and the oil begins to separate at the edges of the masala.

Add the turmeric powder, red chili powder, coriander powder, and salt, and sauté the masala until the spices are fully toasted and fragrant.

Fold the mashed eggplant into the masala, mix well, and let the bharta simmer so the flavors combine.

Turn off the heat, sprinkle the chopped coriander leaves over the bharta, and give it one final stir before serving.