Roast the brinjal on a medium flame till well cooked and the skin has charred completely. Cool, peel and mash.Heat the oil in a non-stick pan and sauté the onions till light golden brown. Add the tomatoes, salt and chilli powder, and sauté till the masala is cooked and the oil rises to the surface. Add the mashed brinjal and mix well. Lower the heat and cook for four to five minutes. Add the chopped coriander and mix well. Serve hot.