firstly, in a large kadai add cubed potatoes, onion petals add water.
simmer for 15 minutes.
furthermore, add tamarind juice, curry leaves, jaggery, turmeric and salt to taste.
mix well and boil for 5 minutes.
furthermore, add cooked dal add prepared masala paste. mix well.
simmer for 5 minutes.
meanwhile, heat oil in small kadai and add mustard seeds, urad dal, dried red chilli and curry leaves.
allow the tempering to splutter then pour over prepared sambar.
finally, udupi sambar / potato onion sambar is ready to serve with plain rice, dosa or idli.