rasam can be started anytime after you have introduced all the spices...however, below spices are ok to start at 6month,,,when it comes to spices,,lesser the better,,go slow with it.
here is what my couple south indian friends used to give to their 6monhts andonwards babies.
i gave it once,it was tasty.
Cooked toor dal - 4 tbsp/5tblsp
a couple diced/tomato or its paste (before giving any new vegetable, try offering it to baby seperately, to know if your baby is ok with it)
cumincoriander powder - 1 tbsp
Salt to taste
Asafoetida powder - a pinch
Turmeric powder - 1 tsp
1 tbsp ghee
Mustard seeds - ½ tsp (remove before serving your baby)
Cumin seed (jeerakam) - ½ tsp (remove before serving your baby)
Coriander leaves - 5 (remove before serving your baby,,avoid choking)

Put the tomatoes in an empty small vessel and smash them. or dissolve the paste in some water,,
2.do tadka of all the spices above and add water,let it boil.
3. Allow it to boil for 10 minutes. When a good aroma arises, pour the cooked toor dall in the rasam mixture and allow it to boil for 1 minute.
add water acc to your baby preferences of soupy texture...
also, if u are gving only salt,,add tomatoes, salt,and some tadka, and toor dal with water,,,eliminate spices,if so.
good luck and njoy..

rama replied. hetal, i prepare the same way :) for my 6month old. rama replied. hetal, i prepare the same way :) for my 6month old.