Heat oil in a non-stick pan, add cumin seeds and asafoetida and sauté till fragrant. Add green chillies and ginger and sauté for a minute.
Add purple yam and sauté for 3-4 minutes. Add coriander powder, turmeric powder, red chilli powder, cumin powder, salt and mix well and sauté for a minute.
Break the wadis and add to the pan. Add lemon juice and coriander leaves and mix well.
Transfer into a serving bowl and serve hot.