Dice potatoes and capsicum into medium cubes.
Heat oil in a skillet, crackle cumin seeds, and sauté sliced onions until soft.
Add potato cubes, turmeric powder, and salt; cover and cook on low heat for 10 minutes.
Add diced capsicum and red chili powder; stir-fry uncovered for 5 minutes.
Sprinkle amchur powder over top and serve warm with phulkas.