Heat a cast iron skillet or Dutch oven over high heat with olive oil. Season roast on all sides with spices. Place in skillet and sear on all sides until well browned.
Place roast in roasting pan (or leave in Dutch oven) and top with onion soup mix, being sure to press it into the roast. Top evenly with apple cider vinegar.
Place drippings in a saucepan and bring to a simmer. Make cornstarch slurry and slowly whisk in and let gravy thicken. Repeat with slurry until gravy is at your desired consistency.
Slow Cooker Version:
– Follow prep directions including searing the roast, but place everything in the slow cooker and cook 7-8 hours on low or 3-4 on high.