Wash and soak beans for one hour or more.
In a small bowl, mix the ginger, green chili, coriander powder, turmeric, and 3 tablespoons of water to make a paste.
Heat the oil in pressure cooker on medium heat. Test the heat by adding one cumin seed to the oil; if seed cracks right away oil is ready. Add the cumin seeds as they crack add asafetida, add the spice paste and stir for a minute until spices start leaving the oil.
Add Black Eyed Beans, salt and water close the pressure cooker as pressure cooker starts steaming turn the heat down to medium and cook for 6-7 minutes.
Turn off the heat and wait until the steam has stopped before opening the pressure cooker. Black-eyed beans should be soft and tender.
Add mango powder, garam masala, and tomatoes, and cover the cooker for a few minutes. That will give tomatoes a chance to get semi-cooked with steam.
Garnish this with lemon wedge.