In a blender, blitz the onion, red chilli pepper, ginger, and garlic together until it becomes a paste.
Set the Instant Pot to Sauté mode and heat the oil.
Add the paste and fry for 4 to 5 minutes until it softens.
Then add the turmeric, cumin, garam masala, coriander, and chilli powder. Sauté well for a few minutes so the spices release their flavour.
Add the chicken and make sure each piece is coated in all the spices and paste. If anything is sticking to the bottom, add a splash of water to deglaze the bottom.
Add the tomatoes and combine well.
Stir in the salt and pepper.
Place the lid on top of the Instant Pot, and set to Pressure Cook mode on high for 5 minutes. Once done, let the pressure release naturally for 5 minutes.
Stir in the lemon juice.
Sprinkle chopped coriander on top and serve immediately.