Wrap the whole zucchinis tightly in foil and place on a grate over hot coals. Cook, turning frequently, until zucchini are very soft. Remove from heat and cool slightly.
Unwrap zucchinis and cut them in half lengthwise. Scoop out the flesh with a spoon and set it aside in a bowl.
Heat the oil in a large pan and cook the onion until golden. Add the chile and garlic and cook another minute. Stir in the coriander, turmeric, and salt.
Add tomatoes and cook until most of the juices evaporate. Add the zucchini and mash it up if there are any large chunks. Cook, stirring occasionally, for another 10 minutes. Mix in the chopped cilantro.