In a large skillet heat the oil over moderate heat until it is hot but not smoking and in it cook the mustard seeds, covered, stirring occasionally, until the popping subsides. Add the gingerroot and the turmeric and cook the mixture, stirring, for 30 seconds. Add the cauliflower, stirring to coat it with the oil, and 1/2 cup water and steam the mixture, covered, adding more water a few tablespoons at a time if it evaporates, for 6 to 10 minutes, or until the cauliflower is just tender. Season the cauliflower mixture with the lemon juice and salt and pepper and stir in the coriander. Serves 6. Gourmet March 1991