Heat oil in a medium frypan over medium heat, and cook the mustard seeds until they begin to crackle. Mix in asafoetida. Reduce heat to low, and mix in onion, garlic, cumin seed and turmeric. Cook and stir until onion is tender, about 5 minutes.
Stir tomato and okra into the mixture. Gradually mix in chili powder, amchoor, and salt. Cook and stir about 10-15 minutes, until okra is tender but firm.