This Maharashtrian side dish has some variations, depending on personal preference, such as one where the onion is stirred in raw or another where a tempering of mustard seeds is added on top. I like the sweetness of cooked red onion combined with the tang of tomato in this recipe.
Place the eggplant on a gas stove without brushing with oil. Turn from time to time (for roughly 7 to 8 minutes) with a pair of tongs until you can pierce the thickest part easily with a knife. By this time the skin will look crinkly and crisp. Let cool then peel off skin with a small knife or with your fingers.
Discard the stalk and mash the flesh of the eggplant in a bowl with a fork. Set aside.
Heat the oil in a skillet over high heat, add the onion and cook for 7 to 8 minutes until soft. Add the chile, cilantro, tomato, and salt to season, then add the mixture to the mashed eggplant. Mix in the yogurt and chill before serving.