Sauté roast: This step allows for a darker, fuller sear and a deeper beef flavor. Season the roast with salt and freshly-ground black pepper. When it's browned, take the roast out of the Instant Pot for a bit to cook the vegetables.
Soften vegetables: Add chopped onion and garlic to the Instant Pot, and cook for 2 minutes. Use a wooden or rubber kitchen spoon to stir regularly and to pull the browned bits from the bottom of the pot. There's so much flavor in that browning.
Cook the roast: Put the roast back in the Instant Pot, and add pepperoncini peppers, beef broth, ranch seasoning, and butter. Put the lid on, set to Pressure Cook, and let the roast braise.
Release pressure: Skip the quick release. Instead, let the Instant Pot release pressure naturally; the pot lid will remain locked until this process ends, and it can take 10-12 minutes. Remove the lid when you’re able to do so.
Serve: Remove the roast itself from the Instant Pot, and put it in a deep ceramic serving platter. Add the liquid from the pepperoncini to the liquid in the Instant Pot, and stir to fully combine. Use your tongs to pull the cooked veggies out of the broth, and layer them on top of the meat. Ladle the broth on the meat and veggies.