Drain, refresh, combine both the lentils. Cook in a pressure cooker, instanpot or directly in a pot until all fully cooked and soft. Check the instructions on the manual for cooking times. Chana dal will cook faster, but we want it to be very soft almost disintegrating. Set aside.
In a separate pan warm the oil or ghee and add cumin seeds. Once they sizzle add the chopped onions and allow to soften for about 4-5 minutes. Now add minced garlic, ginger and chopped green chillies. Saute for a minute.
Add the tomatoes, turmeric, red chili powder, salt to taste and coriander powder. Mix well and saute for 2-3 minutes. If the mixture dry you can sprinkle a few teaspoons of water. The tomatoes should be soft and the raw smell of turmeric should have disappeared.
Add the cooked lentils and bring it up to a boil. Simmer for 5-7 minutes adding a little water to a achieve a desired consistency. Garnish with chopped cilantro and enjoy with rice or rotis.