In a large bowl wash the dhal in several changes of water; drain. Place the dhal and 2 1/2 cups water in a 2-quart saucepan and bring to a boil. Reduce to a simmer and cook, partially covered, for 30 minutes (45 minutes for yellow split peas), or until the water is absorbed and the peas break up under pressure from the back of a sppon. Check to make sure it doesn't boil over.
When the dhal has finished cooking, heat the oil in a frying pan. Add the mustard seeds to the oil and heat until they pop. When the popping subsides, toss in the dried red chili and curry leaves. After a few seconds, add the onion and fry until light brown. Put in the garlic and fry 1 minute. Next, add the ground masala and fry for another minute. Stir this mixture into the dhal, along with 1/2 cup water and the salt. Partially cover and continue simmering another 10 minutes, adding more water if the mixture is too thick. It should be the consistency of thick pea soup. Remove from the heat.
Stir in the lemon juice and ghee. Taste for salt.
Recipe courtesy of Savoring the Spice Coast of India, Maya Kaimal, HarperCollins