Soak the black eyed beans for about 6 to 8 hours. Drain the water and pressure cook (or cook by your method of preference) till soft and done but not mushy. A quicker way of cooking the beans without soaking is cover the beans with enough water (about 2 inches above the beans) and adding a very small pinch of baking soda and then pressure cooking the beans. Keep aside.
Heat the oil in largish saucepan and sautxe9 the onion till it turns golden brown. Turn down the heat to medium, and add the ginger and garlic pastes and sautxe9 for another couple of minutes till the raw smell of garlic disappears. Now add the spice powders and sautxe9 for a couple of minutes.
Add the purxe9ed tomatoes and cook till soft and it disintegrates, about 3 to 4 minutes. Add the black eyed beans, the water and salt. Mix and bring to a boil, then turn down the heat so it simmers. Let the stew simmer for about 10 minutes.
Stir in the coconut milk, and stir well and take the stew off the heat. Do not let the stew boil vigorously after adding the coconut milk or it will split. Add the tamarind paste lime/ lemon juice and mix well. Pour into a serving bowl, garnish with the chopped coriander and serve hot with rice, bread (pao or poee) or chappathis.