Soak tamarind with little water and make tamarind juice.
Skin the plantain and cut into 1/2 inch cubes.
Heat a pan add tamarind juice, cut plantains, turmeric powder, chili powder, salt to taste and cook them for 4 to 5 minutes NOTE: add water if needed, plantain should not be cooked so its become mushy.
Heat oil in a pan add mustard seed and split black gram. Wait until the mustard seed stop splattering.
Now add the cooked plantain, sauté and cook in low heat Until Oil is well coated and plantain is fried NOTE: don't break the plantain.