Rinse the dals and soak for 30 minutes. You can do one kind of dal, all three, even more than three...it's your life and your dal! Soaking isn't absolutely necessary, but it helps cook faster and results in a smoother dal.
Pressure cook the dal with water. In an electric pressure cooker like the Instant Pot, pressure cook on high for 6 minutes. Allow for a natural pressure release. In a regular pressure cooker, it should take 4-5 whistles over medium heat. Alternatively, you can simmer the dal in the pot that you prep the aromatic tomato mixture (next step) in!
In a pot over medium heat, add oil. Add cumin seeds, mustard seeds, and hing. Let the seeds sputter for a minute, stirring frequently. Add ginger, garlic, and green chilis. Cook until garlic starts to brown, so about 2 minutes. Add onions and cook until translucent and browned, so about 4-5 minutes.
Add tomatoes and a big pinch of salt. When the tomatoes clump together in the pot, add garam masala and red chili powder. Add the pressure cooked dal to this pot. Adjust the amount of water and salt if necessary!
For the tadka, heat vegan butter or oil in a small pan or ladle over medium heat. (Or medium-high heat for best results. Make sure not to burn the spices!) Then add cumin seeds, dry red chilis, kashmiri lal, and hing. This is called tempering your spices and the process goes by very quickly (within a minute). Immediately add the tadka to your dal.