Ingredients

• 5 tablespoons picked-over split skinned toovar dal (a variety of pigeon pea, usually descibed as as yellow lentils)
• 4 cups water
• 1 1/2 tablespoons ghee
• 1 1/2 teaspoons black mustard seeds
• 1 fresh hot red chile such as serrano or Thai, halved lengthwise
• 1 1/2 pounds plum tomatoes, seeded and chopped
• 2 tablespoons finely chopped peeled fresh ginger
• 1 teaspoon ground coriander
• 1 teaspoon tamarind concentrate
• 3/4 teaspoon turmeric
• 1/2 teaspoon ground cumin
• 1/2 teaspoon asafetida powder
• 3 fresh hot green chiles such as serrano or Thai, halved lengthwise
• fresh cilantro sprigs

Instructions

1. Wash dal in several changes of water until water runs clear and drain well in a sieve. Cook dal at a bare simmer in 1 1/2 cups water in a 3-quart saucepan until most of water is evaporated and dal has consistency of a paste, 40 to 45 minutes, stirring frequently during last 15 minutes to prevent scorching.
2. Heat ghee in a 6-quart heavy saucepan over moderately high heat until hot but not smoking, then cook mustard seeds and red chile, stirring, until seeds begin to pop. Add 1 1/2 cups water and remaining ingredients (but not dal paste). Bring to a boil and simmer, stirring occasionally, until tomatoes are softened, 6 to 8 minutes. Add dal paste and remaining cup water, stirring to incorporate. Bring rasam to a boil, stirring occasionally, and season with salt.