In a pressure cooker or a saucepan, add oil and heat over medium heat. When the oil is hot, add the mustard seeds and cumin seeds. Let the mustard seeds begin to pop. Depending on the pan and stove it can take 1 to 2 minutes.
Add the asafetida and mix in. Add garlic, ginger, chili and onions and mix. Cook for a minute. Add a pinch of salt and mix in, reduce heat to low-medium and continue to cook until the onions and garlic are golden brown. Stir occasionally. Lower the heat if the onions start to brown too quickly. All of the onion and garlic should get golden, and the onion pieces will reduce in size. a patient 8 to 9 minutes.
Add in the ground spices and mix in. Cook for 15 seconds. Add the tomatoes and a splash of water. Cover, increase heat to medium and cook until the tomatoes are saucy. 6 to 7 minutes. Stir once and mash the larger pieces.
Drain the lentils that have been soaking, and add to the pan. Add water and salt and mix in.
Pressure Cook/Instant pot: Close the lid and cook for 12 to 13 minutes at high pressure. ( 2 whistles over high heat, them simmer for 10 minutes over low heat). This will make mushy lentils.
Saucepan: Cover and cook over medium heat for 20 minutes. Reduce heat to medium-low and simmer for 15 minutes.