I can never imagine making a sambar without lentils, PERIOD! Pressure cooked, mashed lentils is used mainly for getting thicker consistency. So, when I had this thakkali sambar at my friend's place, I simply couldn't believe that the sambar hadn't use any kind of lentils / thickening agents.
Infact, I did not believe until I tried it for myself. And YES, this sambar is one of the quickest & easiest recipes around that goes with any kind of south-Indian breakfast.