Bring toor dal and 3 cups of water with turmeric to a boil. Reduce to a simmer and cook for 45 minutes - 1 hour, until tender. Using an immersion blender, puree.
Dissolve tamarind paste in 1 1/2 cups boiling water and leave for 15 minutes. Drain tamarind extracting all the liquid.
Heat oil in a pot. Add onion and saute until softened.
Add tomato, okra and cauliflower with 2 cups water and sambar powder. Bring to a boil and cook for 10 minutes.
Add tamarind and pureed dal. Cook for 10 minutes.
In a small skillet, heat 1 tablespoon of ghee. Add asoefetida and mustard seed. Once they stop popping, add cumin seed, fenugreek, chiles and curry leaves. Fry for 1 minute.
Add to sambar and cook for 1 more minute. Add cilantro and salt to taste. Stir to combine.