Rinse dal well. Soak dal for about 1 hours, this helps in cooking dal faster. Once soaked, discard the water from the dal and add fresh water. Add cloves, cumin seeds, turmeric powder and 1 teaspoon oil to dal and pressure cook it for 2 whistles.
While dal is cooking, you can make the tiffin sambar powder. In a pan dry roast red chilies, cumin seeds, fenugreek seeds, Bengal gram, black pepper corns one by one until roasted well and turns fragrant. Let the roasted spice cool down, and then grind into fine powder. You can store this tiffin sambar powder in air tight container for a few months.
In a kadai, heat oil. Once oil turns hot add curry leaves and chopped shallots and sautxe9 till onions turns translucent.
Add chopped tomatoes and cook until tomatoes turns mushy.
Add red chili powder and 3 to 4 tablespoon of tiffin sambar powder and salt to taste, give it a mix.
Add cooked and mashed dal to the kadai and bring it to boil. Check for seasoning and adjust according to your taste.
Add tamarind juice and let it boil for 3 to 4 minutes.
Turn off stove, sambar is ready, we need to add the tempering to the sambar now.
In a small pan, heat oil. Add mustard seeds and let it crackle. Add thin onion slices and sautxe9 till onions turn golden brown. Add curry leaves, dried red chilies and asafetida, mix well. Remove from stove and add this tempering to the sambar. Give it a mix.
Serve tiffin sambar with idli, dosa or even pongal. The best way to serve this sambar is with hot idlis in a bowl, dribble some ghee and pour hot sambar on it. Pure bliss!