In a pressure cooker, combine toor dal, green tomatoes, eggplant,, turmeric powder, salt and 1½ cups water.
Place over medium heat and cook till 1 whistle or 20 minutes till dal and veggies have turned tender. Don't over cook the veggies.
Place a non-stick pan over medium heat, add all the ingredients mentioned 'to roast and grind to a coarse powder' and roast till coconut turns golden brown.
Let cool down and grind to a coarse powder.
Open the pressure cooker, combine the cooked veggies and toor dal.
Add turmeric powder and ground masala, combine well.
Add ½ cup more water.
Cook for 5 minutes and remove from the heat.
Place a frying pan over medium heat, add 2 tbsp oil and let oil turn hot.
Add mustard seeds, let it splutter.
Add dry red chilies and curry leaves, fry for a few seconds.
Pour the tempering over the cooked sambar.
Close the cooker with its lid and keep aside for 5 minutes.
Serve sambar along with idli, dosa or rice, tastes delicious.
Notes
Roasted Ground Masala can be made ahead of time and refrigerated in an air tight container for a month.
Recipe by Cooking with Thas - Smart Cooking, Smart Living at https://thasneen.com/cooking/green-tomatoes-sambar-south-indian-recipe/