Dice the skinless boneless chicken breasts into 1 inch cubes, keep them in a bowl. Add all the ingredients mentioned above in the "For making Chicken Tikka" section into the bowl. Rub well to coat all the chicken pieces with the marinade. Leave for 30 mins before you begin air frying them.
Set the Instant Pot, do not plug it. Place the air fryer basket inside the steel insert of the Instant Pot.
Throw in the cubed onion pieces in a single layer inside the air fryer basket. Spray with oil.
Now, place the air fryer steel disc insert inside the air fryer basket. Spray the disc with oil and arrange the marinated chicken pieces in a single layer. Do not over crowd and leave a few openings (holes) on the metal disc open (refer the video or steps pics above). It's a must for hot air circulation.
Spray the chicken pieces with oil. Put the air fryer lid on. Plug it.
Hit the AIR FRY button and set the temperature to 350 F and the time to 6 minutes. Hit the START button to begin air frying the chicken tikkas.
Once, the air frying cycle is over the Instant Pot will begin to beep. Hit the CANCEL button and carefully open the lid (it's very very hot) and place it on the heat proof base that comes along with the air fryer lid. DO NOT place it anywhere else because it's super hot!
Now, if you prefer the charred look on the chicken tikkas go ahead and char the chicken tikkas with a torch or you may also put back the air fryer lid and hit the BROIL button to char the chicken pieces for a few minutes. I used a torch for fun :D The beautifully charred Chicken Tikkas are all ready now. Let's make the world's best Tikka Masala Sauce.
Also, remove the air fried onion pieces from the air fryer basket and finely chop them.