If you follow the order in which I list steps, this will come together efficiently. So first rinse the rice and set it aside. This rinse will allow the rice to soften a bit and absorb some water.
Into a bowl, pour all the ingredients for the marinade, along with the lamb.
Let the lamb marinate for 30 minutes, while the rice rests. This is a good time to get the onions for the garnish together.
Turn your oven to broil. Line a baking pan with foil.
Thinly slice your onions and break apart the slices with your fingers. Lay these on the foil covered pan, add salt and the oil, and mix well.
Broil these onions for about 15 minutes stirring only once or twice. Traditionally this is done in a pan on the stove, but it's quite a painstaking process. This method is largely hands-off and works well.
By this time, your lamb has probably marinated and you're ready to put it all together.
In the inner liner of your instant pot, spread the marinated lamb, yogurt and spice mixture to cover the bottom.
Carefully spread the rice all over the meat in a uniform layer.
Pour in the 1 cup of water and gently push down the rice until it's submerged under water. Do not mix the lamb and the rice together.
Cook at High Pressure for 6 minutes and allow it to fully release pressure naturally. This part is important, here is where we are approximating the "dum" (steam cooking) part of the Dum Biryani.
Open and garnish with 1/2 cup chopped cilantro and the browned onions.