How to Make It
Preheat the oven to 375°. In a small bowl, combine the sumac, rosemary and pepper. Drizzle the roast generously with olive oil and season with salt. Rub the garlic and the spice mixture all over the roast and let stand for 10 minutes.
Using butcher’s twine, tie the roast at 1-inch intervals to give it a uniform shape. In a medium ovenproof skillet, heat the vegetable oil. Add the roast and cook over moderate heat until lightly browned all over, about 12 minutes.
Transfer the skillet to the upper third of the oven and roast the meat for about 1 hour, until an instant-read thermometer inserted in the center registers 130°. Transfer the roast to a carving board and let rest for 10 minutes. Discard the twine. Using a thin, sharp knife, thinly slice the beef across the grain and serve.
Ground sumac is available at specialty stores and online at penzeys.com.