Heat your Instant Pot to sautee mode. Add the onion and cook until it begins to soften, about 2-3 mins. Then, add the cumin, cinnamon and nutmeg and cook until fragrant, about 1 minute.
While the onions cook, place the broth and dates in a large microwave-safe bowl and microwave until the broth is very hot, about 1-1.5 mins
Place the broth and date into a food processor and process until the date is mostly broken down - a few little pieces are okay. Then, add in the tahini, lemon and salt and process until combined.
Once the onion is done, season the chicken with the za'atar. Place it into the bottom of the Instant Pot.
Pour the sauce over the chicken. Cover and set the lid to sealing. Cook for 10 mins on manual high pressure.
Once cooked, do an instant steam release. Transfer the chicken to a cutting board.
Turn the Instant Pot to Sautee mode and cook, stirring frequently, until the sauce thickens. About 5-10 mins.
Shred the chicken and stir it back into the pot.
Garnish and DEVOUR!