Soak the uncooked rajma beans in water overnight - for at-least 6-8 hours.
Drain all the excess water in the morning, rinse well, and pressure cook the rajma beans with a little over double the quantity of water for 4 whistles.
Set the pressure cooked rajma aside, retaining the water in which the beans were cooked, to use in the curry later.
Making the Masala Base
In a pan - heat up the oil, add in chopped onions and salt, and mix well. Saute till the onions start turning light golden brown.
Then add ginger garlic paste, mix well, and saute for 2-3 minutes, just until the paste loses the raw flavor.
Now it’s time to add the masalas - rajma masala powder, garam masala powder, coriander powder, chilli powder & cumin powder. Mix well and saute for 1-2 minutes on medium heat. If required, sprinkle some water to avoid the masalas from burning.
Finally, add in the chopped tomatoes, mix well, and saute on medium low flame, till you see the oil leave the sides. Then turn off the gas, and let the onion tomato spice mix cool for a bit.
Pureeing The Masala Base
Once the spice mix has cooled down, puree it in a blender, along with some fresh water, and a few spoons of boiled rajma beans, till you get a smooth paste like consistency.
Making Rajma Curry
Once the puree is ready - pour it into a pan. To this pan, add the boiled rajma beans along with the retained water, some more fresh water, and mix well. At this point also taste for salt, and adjust accordingly.
Then let the rajma curry simmer on low heat for 15-20 minutes, stirring intermittently, before turning off the heat.
The Rajma Masala is now ready to serve with roti / naan or rice.
Notes
If you have forgotten to soak the rajma beans overnight, and need to make this dish really quickly, you can either boil the rajma beans in 2 cups water & let it power soak for 2 hours & proceed as normal. Or you can simply pressure cook raw (unsoaked) rajma beans for a few additional whistles (above the recommended 4 for soaked or power soaked rajma beans). Either of these methods will work in a pinch.
Boiled rajma beans should mash easily with minimal pressure when pressed by hand but still hold form. This will ensure the rajma beans will not have a bite and will have that melt in mouth quality.
In this recipe, I have pureed the onion tomato base, but you can skip it if you like a chunkier curry. You can also use chopped onions along with tomato puree. Adapt the texture to your preferences.
However if you do choose to puree the base, add a few tablespoons of boiled rajma beans while grinding to help the rajma beans bind better with the curry and also make the curry more creamier.
Adjust spice level to your palate. I always add additional masalas if I am using store bought rajma masala powder. If I am using homemade rajma masala powder, then that’s usually the only spice powder I use.
If you want to use canned rajma beans, then use 2 cups of canned beans for this recipe.
This dish is a good candidate to make ahead as it gets tastier a few hours or a day after it is made, once the rajma beans have had a chance to sit in the curry and absorb all the flavors.