Pressure cook toor dal with 1 and 1/2 cups of water. Once cooked, set aside.
In a pan, dry roast all the ingredients (except coconut) on low flame till you get a nice aroma. Add grated coconut and roast for 3 more minutes. Switch off the flame. Allow it to cool and and grind to a fine powder.
Heat oil in a pan, splutter mustard seeds. Add curry leaves and asafoetida and saute for a few seconds. Add chopped onion and saute till transparent. Add chopped cauliflower, carrot, and potato and saute well. Add the ground masala powder and mix well. Add tomatoes and saute well. Add cooked toor dal, a cup of water and salt. Bring to a boil, lower the flame, close the lid till the vegetables are 3/4th cooked. Now add the tamarind extract along with a cup of water. When vegetables are fully cooked and the gravy thickens, switch off the stove. Transfer the kootu to a serving bowl.