Make your marinade. Mix 2 tbsp of oil, lemon juice/zest, coconut milk, oregano, salt, pepper, and garlic powder together.
In a container with a lid, put lamb and marinade inside. Refrigerate your lamb mixture. 24 hours is great but at least for 8 hours.
In your Instant Pot, with the sauté feature on put 1 tbsp of oil in your pot. Sear each side of your lamb for 5-6 minutes. Reserve the leftover marinade.
Take out the lamb and put it on a plate or in a bowl.
Put your diced onion into the Instant Pot. Sauté onion for 5 minutes. Season with a pinch of salt.
Add in your 1/2 cup of broth to deglaze the pan. Scraping up the bits at the bottom of the pot.
Add in the rest of your leftover marinade. Mix well.
Put the lid onto your Instant Pot. Set your IP to high pressure for 1 hour. Can go up to 90 mins if you have a really large cut of meat.
Let it naturally release for 15 mins.
Let the rest of the pressure/steam out.
Take it out of the pot and let it rest for a few mins. Cut into pieces and serve. Add additional salt/ pepper if needed.