Heat the oil in the non-stick pan over medium heat. Add the mustard seeds and toast them until they start to pop.
Add the cumin seeds and allow them to sizzle. Then add chopped green chilis and asafoetida and stir well.
Add diced bell peppers and mix well. Then, add salt, turmeric powder, red chili powder, cumin powder, and coriander powder and mix well to combine.
Sprinkle a few drops of water into the pan, and continue to cook the green peppers on medium heat.
Cook them for 6-8 minutes, until the bell peppers are crisp-tender, stirring occasionally.
Sprinkle one tablespoon of roasted besan all over the Sabji and mix well. Then, gradually add the remaining besan and mix well after each addition.
Add one or two tablespoon of water to the Sabji and mix well to coat the peppers with the besan. Continue to cook for 5-6 minutes, stirring occasionally, making sure the besan does not burn.
Finally, add sugar, amchur powder or lemon juice, crushed peanuts, and chopped coriander leaves. Mix well, taste, and adjust the salt as needed. Turn off the heat and serve the Sabji hot.