Ingredients 

1. Toor dal (kandi pappu) - 2 cups
2. Tamarind - big lemon sized piece or 2 spoons of paste
3. Onions - 1 big
4. Tomato 1 medium
5. Salt - as required
6. Chilli powder - 1/2 spoon
7. Turmeric (pasupu) - 1/2 tsp
8. Sambaar powder - 1 1/2 to 2 tsp
9. Coriander leaves - few
10. Seasoning - 1tsp of mustard seeds, 1/2 tsp of jeera, pinch of hing, few curry leaves

Method: 

Put dal in pressure cooker, add double quantity of water and cook until 3 whistles.
If using tamarind piece, soak in some water then take juice of it.
Take a big vessel add some oil (3 spoons), after heated add onion pieces fry for some time, add turmeric and add the tamarind juice (or tamarind paste in to the onions then pour 1 or 1 1/2 cups of water).
After tamarind water starts to boil add chilli powder, sambaar powder, salt and allow it boil for some more time.
Now add cooked dal ( mashed with back of a spoon) mix properly into tamarind water and allow it to boil for some time . Add chopped tomatoes and coriander leaves if desired. Taste for salt and spiceness and add little if required . Reduce heat and boil for some time and switch of the stove.
Add coriander leaves according to your taste.
Put small fry pan on stove and add 2 spoons of oil. After heated add red chilli pieces, inguva, curry leaves, mustard seeds, jeera and switch off the stove. Add this to the sambaar.