Soak tamarind in 1/4 cup of water and get thick juice.
In a pan heat oil, add mustard seeds, split bengal gram, split black gram, dry chili, curry leaves. Once the mustard seeds stop splattering add green chili, onion and cook until onion turns translucent (golden brown).
Now add the brinjal and sauté for 5 minutes.
Now add tamarind juice, chili powder, asafoetida powder, turmeric powder, salt as needed and mix well.
Place a lid, Cook until the brinjal is cooked and oil separates. Should take about 10 minutes. NOTE: stir time to time so it does brinjal masala get burnt.