Season the chuck roast liberally with salt and pepper, then using the sauté setting of the Instant Pot, sear it in a tiny bit of oil on both sides. Throw the sliced onion over the top, seal the Instant Pot (move the small knob on the black top to the sealing setting), select the pressure cooker setting, and set the time for 70 minutes.
You'll see some steam escaping from the small silver round valve on top of the Instant Pot until the pressure builds and it seals. If you see steam coming out of the sides of the lid, you haven't sealed the top properly so let the steam out according to the directions and start again.
Release steam according to the Instant Pot directions, then remove the roast and serve
Recipe by Cooking With Michele® at https://cookingwithmichele.com/2019/01/instant-pot-roast/