firstly, heat 2 tbsp oil and saute 20 small onion, 3 clove garlic and 1 chilli for 2 minutes.
add ¼ tsp turmeric and 1 tsp salt. saute for a minute.
further add 1 tomato and saute well.
now add ¾ cup tamarind extract and 1 cup water.
cover and boil for 10 minutes or until raw flavour are gone.
add 1½ cup toor dal and mix well adjusting consistency as required.
further get to a boil for 2 minutes.
add 3 tsp prepared sambar powder and 1 tsp jaggery.
mix well and boil for a minute.
prepare the tempering by heating 2 tsp oil.
splutter 1 tsp mustard, ¼ tsp methi, few curry leaves, pinch hing and 2 dried red chilli.
pour the tempering over sambar.
add 2 tbsp coriander and mix well.
finally, enjoy onion sambar with hot steamed rice.