Quick hack to use different dals in your rasam recipes. These are instructions for adding thoovaramparuppu/arhar/toor dal in the upliance recipe.
These instructions use 2 recipes - Tomato Pappu & Rasam and make a little addition:
Open the Tomato Pappu recipe, it has instructions on how much dal, in how much water, and how to pressure cook.
While the dal is being cooked, follow the Rasam recipe on your upliance.
Add 1 small spoon of split urad dal along with curry leaves and mustard seeds
Add the strained and cooked toor dal, at the Tamarind paste step
I’ll also suggest you skip the jaggery in this variation