Add butter to Instant Pot and melt using saute button.
Add onion to butter and cook 1-2 minutes, until onion softens.
Add rice to Instant Pot and stir, cooking 1-2 minutes until rice begins to take on a translucent quality.
Pour hot broth into pot.
Seal lid and set cook time for 5 minutes.
Do a quick pressure release at end of cook time.
Remove lid when pressure is released. If there's a lot of liquid, use the saute button to cook off a bit of the liquid. You don't want it to be dry, but it shouldn't be too soupy either.