Cut pot roast into smaller pieces- about 4 inch by 4 inches.
Once pot is hot, place the roast into the oil and sear on all sides. This should take 3-4 minutes per side.
Once roast is seared and browned on all sides, remove roast from pot and set aside.
Add onion to pot- stir continuously.
Be sure to "scrape" the browned bits off the bottom and sides of the pan while you are stirring the onions. Use a plastic or silicone spoon or spatula. Do not use a metal utensil or you will scratch the Ninja Foodi pot.
Once onions are translucent, pour in the garlic and stir for a minute or two.
Add in pepperoncinis and pepperoncini juice and then pour in beef broth
Sprinkle in Hidden Valley Ranch dip mix, Au Jus powder and brown sugar- stir until all ingredients are combined well.
Return the pot roast to the Ninja Foodi pot. It's okay to stack the meat on top of each other.
Top roast with 4 tablespoons of salted butter.
Leave remaining 4 tablespoons of butter on the counter so that it comes to room temperature and softens.
Close the pressure cooker lid and move valve to "seal."
Cook oh high pressure for 65 minutes (1:05 hours)
Combine remaining 4 tablespoons of butter (½ stick) with ¼ cup of flour. Be sure that the butter is room temperature so that it combines easily with the flour. Mix thoroughly. If the mixture is lumpy, your gravy will be VERY lumpy too. (I made this mistake the first time).
Once timer goes off, let pressure naturally release for at least 15 minutes and then quick release remaining pressure by moving the valve to "release."
If liquid starts to come out of the valve, close valve to "seal" position and naturally release more pressure.
Remove roast from pot and put in serving dish
Turn Ninja Foodi off and then back on to sauté function- let simmer for 3 minutes
Add butter and flour mixture to the pot. Whisk to combine all ingredients well. This will help to thicken and smooth the gravy.