2) Heat a nonstick pan over moderate heat. Add the cumin seeds and stir until they start to crackle (about 10 seconds). Then add the onion, ginger and garlic. Stir until onions are translucent. Add turmeric powder, coriander powder and red chilli powder. Cook, stirring, for about 20 second. Then add the tomatoes or tomato sauce. Bring to a boil, reduce heat and let simmer for 1 minute.
3) Add chopped and puréed chana dal. Cook, while stirring, 2-3 minutes to allow flavors to blend. Then add salt to taste. Remove from heat. Add lime or lemon juice and stir.