Rinse and soak the red kidney beans in enough water for 1 - 2 hours. After 2 hours, discard the water and drain beans in a colander. Set aside.
In a pressure cooker heat oil over medium heat. Add the chopped onions, asafoetida and ginger-garlic paste, saute till onion turn caramelized and light brown in colour. Keep on stirring the onions while sauteing them, for uniform cooking and also so that they don't get burnt.
Next, add the drained beans in the pressure cooker along with salt, chopped tomato and turmeric powder. Stir to combine and saute the mixture for 2 - 3 minutes.
Add the 4 Cups of water to the pressure cooker, close the lid, put the weight and let beans cook over medium heat for 2 - 3 whistle. Turn off the heat.
Let the steam release naturally from the pressure cooker. Check if the rajma is cooked or not by taking a bite or pressing a bean. If they are not fully cooked completely, then pressure cook again or simmer over low heat for few more minutes. Meanwhile add some water if required to adjust the consistency of the curry.
Simmer rajma masala without a lid for 10 -12 minutes or more till the curry thickens slightly, it should not be watery.
Add red chilli powder, garam masala and green chillies. Mix nicely. Mash a few rajma beans with the back of the spoon, this helps to thicken the curry.
Serve rajma masala with steamed basmati rice or jeera rice for lunch.
Cooking time of rajma may vary according to the quality and size of the bean. It is best to check it for doneness after few whistles.