Like dals all over India, making this soup requires that you cook the lentils until they are the desired texture and then add a mixture sauteed in ghee (clarified butter) that usually consists of onions, garlic, chilies and whole spices like cumin and mustard seeds. Other possibilities are curry leaves and asafoetida (a really smelly powder that tastes somewhat like onions and garlic)
Rasam in it's many variations is a year round favorite in Southern India... and it is also used as a folk remedy for a variety of cold and flu like symptoms. I can speak from experience... this nice spicy broth really clears your head and make you feel better when your feeling under the weather.
Here is what I did to make mine....
First I gathered together my ingredients:
1/2 C. pink lentils (washed several times and then soaked in 1 cup of water for 30 minutes)
1/4 t. turmeric
1/2 t. salt
a good size chunk of fresh ginger (grated)
1-3 green chilies
1 medium tomato
2 whole dried red chili peppers
1/2 t. black mustard seeds
1/2 t. cumin seeds
1/2 t. black pepper
1 small onion
a few cloves of garlic
2 T. lemon juice
1/2 C. chopped cilantro
Transfer lentils with soaking water into a pan and add turmeric. salt and 2 more cups of water. Bring to a boil and cook over medium-low heat for 20-30 minutes. The dal should be very soft at this point. I then used a hand held mixer to make the mixture as smooth as possible. in the meantime blend the tomatoes, ginger and chilies for about 30 seconds in a blender. Add to the dal to make approximately 4 cups of soup. Simmer for another 5 minutes or so.
Heat oil or ghee and cook the mustard and cumin seeds until they begin to pop. Add the onions, garlic and dried chilies. Cook until the onions are golden and soft.