Marinate Chicken: Begin by combining your marinade ingredients in a bowl. Stir well and add in cubed chicken pieces. Allow to marinate in the fridge for at least an hour.
Turn on your Instant Pot to saute setting-- add butter, marinated chicken pieces, onions, garlic, fresh ginger, curry paste, garam masala, cumin, and salt.
Saute for 5 minutes, stirring constantly to make sure the spices don't burn.Once the onions are soft and translucent, turn off your Instant Pot.
Stir well and then add tomato sauce. Do not stir. (The tomato sauce can sometimes cause the Instant Pot to have a "burn warning." To avoid this, add the tomato sauce to the middle of the butter chicken sauce and don't let the tomato touch the sides).
Cook on High Pressure setting, for 8 minutes.
Allow to vent using natural release.
Add ½ cup of heavy cream. Stir to combine.
Serve with warm naan bread or over rice.