Wash red lentils thoroughly until the water runs clear and soak them in water for 1 hour (soaking is optional). If cooking on the stove top, cover with enough water, cover with lid and cook for 20 minutes. If using a pressure cooker or the Instant Pot, cook the lentils until they turn mushy. Set aside.
Wash rainbow chard well. Separate the stems of the chard from the leaves. Cut the leaves into thin strips. Thinly slice the stems.
Wash and soak tamarind in water for 5 minutes. Crush the tamarind with your fingers to release the juices. Discard the pulp and save the water.
In a thick bottom pan, heat coconut oil. Splutter mustard and cumin seeds. Add finely chopped onions and sauté until onions are translucent.
Add the rainbow chard stalks and sauté for 2-3 minutes, until they are slightly tender but crunchy.
Add the cooked lentils, salt, turmeric, freshly ground black pepper powder, tamarind juice, garam masala powder and chopped tomatoes. Mix well. Add water if the consistency is too thick. Cover, and on a medium flame, bring to a boil, while mixing well once in a while.
Stir in the shredded chard leaves, cover, and cook 2 minutes over medium-low heat. Stir, re-cover, and continue cooking until the chard is tender (about 2 minutes).
Serve hot!
