Switch on the instant pot to saute (normal), and add the oil, followed by the the onion puree prepared earlier. Add the red chilli, turmeric, coriander and garam masala powders. Sauté for 4-5 minutes, adding splashes of water if required.
Add the kidney beans, salt and 2 cups water.
Cancel the saute mode, close the lid, seal the vent and set the timer to 30 minutes, high pressure. When the timer beeps, let the steam escape naturally. Open the cooker and switch to saute mode again.
Mash one or two tablespoonfuls of beans wit the back of a spoon and simmer for 5 minutes so that the beans get mixed with the gravy. Take out the rajma in a bowl.
To temper the rajma curry, heat a tablespoon of oil in a small frypan and add the sliced onions and cumin seeds. When the onions turn reddish brown, add the dry red chillies and pour this seasoning into the bowl of rajma immediately.
Serve hot with some steamed rice and a salad of your choice.