Heat oil in a pan over medium-high heat. Once the oil is hot, add cumin seeds, asafoetida and let them crackle for 30 seconds.
Add green chili, onions and grated ginger. Saute and cook until the onions turn golden.
Add potatoes and stir well. Reduce heat to low, cover and cook for 5-6 minutes. Stir a few times while cooking.
Remove lid and add all the spices. Stir it well. Add tomatoes, stir well. Cover with a lid and cook for about 3 minutes until the tomatoes are mushy.
Remove the lid and add bell peppers and mix well.
Cook for 6-8 minutes until the bell peppers are mostly cooked. You want to leave a little crunch. Turn off heat. Add aamchur and mix gently.
Garnish with cilantro and serve hot with roti.