Cook dal in 4 cups of water until tender. Purée partially, using a hand-held blender or put half in a regular blender. Set aside. Heat a non-stick pan over moderate heat. Add the cumin seeds and stir until they crackle (about 10 seconds). Add onion, ginger, and garlic. Stir until onion is translucent. Add turmeric, coriander, and red pepper. Cook, stirring, for about 20 second, being careful not to burn. Add tomato sauce. Bring to a boil, reduce heat and let simmer 1 minute. Add chopped and puréed chana dal. Cook, stirring, 2-3 minutes to allow flavours to blend. Add salt to taste. Remove from heat. Add limejuice and stir.
Serve over a bed of one-half rice and one-half barley. Top with chutney or fat-free sour cream or plain non-fat yoghurt.