Combine the toovar dahl, turmeric powder, asafetida and 1½ cups of water in a pressure cooker and pressure cook for 3 whistles.
Allow the steam to escape before opening the lid. Whisk the dahl well.
Combine the whisked dahl, vegetables, salt and 1½ cups of water in a deep non-stick pan, mix well and cover with a lid and cook on a medium flame for 20 to 25 minutes, stirring occasionally.
Add salt to taste.
Add the tamarind pulp, 1/2 cup of water and the prepared sambhar masala, mix well and cook on a medium flame for 10 minutes, stirring occasionally.
Add the chopped coriander and mix well and set aside.
Heat the oil in a small non-stick pan, add the mustard seeds. When the seeds crackle, add the curry leaves and red chilies and sauté on a medium flame for a few seconds. Add tempering to the prepared sambhar and mix well.
Serve hot with Idli or Dosa