Season meat with salt and pepper. Turn Intstant Pot on Saute mode.When display says "Hot", add the oil.
Place meat in the hot oil. Let cook for 5 minutees without moving. Flip over and cook 5 more minutes.
Remove meat to a plate and tent with foil to keep warm.
Add onion to pot along with about 1/4 cup of the beef broth. Use a wooden spoon to scrape up the browned bits on the bottom.
Add remaining beef broth, pepperoncinis, pepperoncini juice, Ranch seasoning, Au Jus, and butter. Stir to mix.
Turn the saute mode off and add meat and any juices back to the pot.
Close lid and set knob to "sealing" position. Set to Pressure Cook/Manual for 55 minutes.
When the 55 minutes is up, let sit for 15 minutes for Natural Pressure Release.
After 15 minutes, turn Instant Pot off and manually release remaining pressure until the pin drops. Once pin drops, remove lid from Instant Pot.
To make gravy, remove meat to a plate. In a small bowl, mix the butter and flour to make a paste.
Turn the "Saute" mode on. Once it comes to a simmer, add flour mixture. Whisk until thickened.
Shred meat and return to pot.