How to Make It
In a medium saucepan, combine the thoor dhal and turmeric with the water and bring to a boil. Cover and cook over low heat until tender but not mushy, about 30 minutes. Add the serrano chiles, onion, garlic and ginger and simmer until the onion is softened, about 5 minutes. Add the tomato and salt and simmer until the tomato is softened.
In a small skillet, combine the oil, mustard seeds, curry leaves and dried red chiles. Cover and cook over moderately high heat until the seeds pop. Stir the spices into the dhal and serve.