Pressure cook the dal before hand and cool it down (it makes it faster to get it cooked under pressure)
Saute onion, ginger and garlic on 1 tbsp of oil. Stir it for 2-3 minutes and let the onions start to caramelise. Thereafter add the tomatoes. Once it sizzles for a couple of minutes, bring it to sim and let it cook for another 5-6 minutes. Let it cool for 5-10 minutes and then blend it to a fine paste with green chilly.
Bring the cooked dal to boil. Add all the spices listed above (except cumin seeds) and salt as per taste. Add the cooked tomato ginger onion paste made in step 1
Once the dal is boiling, bring it to low and let it simmer for another 15 minutes. If its too thick, add boiling water in small amounts to the required level of gravy.
Garnish with lightly roasted cumin seeds in a tsp of oil.Can be served as soup or with fresh chapati