Ingredients:

Toor Dal - 3 tbsp
Juicy Tomatoes - 2
Lime Juice - 3 tbsp
Rasam Powder - 2 tsp
Curry leaves -few
Coriander leaves - few
Mustard seeds - for seasoning
Oil - 1 tsp
Red chili -1
Cumin seeds - for seasoning
Garlic - 4 pods
Ginger - 1/2 inch piece
Asafetida - a pinch
Salt to taste

Preparation:

Cook toor dal in a cup of water. Mash it to a fine paste.  Dice and puree tomatoes. Heat a heavy vessel. Add oil and season mustard and cumin seeds, chilies, curry leaves and asafetida. Add the  tomato puree, salt, rasam powder, crushed garlic/ginger and bring it a nice boil. Finally add the mashed dal paste and lemon juice. When rasam starts foaming remove it from heat and garnish with coriander leaves.