Ingredients
3 to 4 pound beef roast (top sirloin, rump, or eye of round), at room temperature
1/2 cup whole grain Dijon mustard (or coarse-ground brown mustard)
2 to 2 1/2 teaspoons kosher salt
Directions
Line a sturdy baking sheet with aluminum foil for easy cleanup and set a wire rack on top if you have one. Let the beef roast sit out at room temperature for about 45 to 60 minutes so it roasts more evenly.
Preheat your oven to 450°F (230°C). Adjust an oven rack to the center position so the roast will sit in the middle of the oven.
Pat the roast very dry on all sides with paper towels. This helps the mustard cling and encourages a good crust. If there is an especially thick fat cap, you can trim it slightly, but leave a thin layer for flavor.
Sprinkle the kosher salt evenly over all sides of the roast, pressing it in gently with your hands so it sticks. This is your only seasoning besides the mustard, so be sure to cover every surface.
Place the salted roast on the foil-lined baking sheet (on the rack if using), fat side up. Spoon the whole grain mustard onto the top and sides of the roast and spread it with the back of the spoon or your fingers. You want a generous, even coat, about 1/8 inch thick, with the mustard grains clearly visible. Leave the bottom mostly bare so air can circulate.
Slide the baking sheet into the preheated 450°F (230°C) oven and roast for 15 minutes. This high heat jump-starts that golden, flavorful crust Earl always talked about.
After 15 minutes, without opening the oven for long, reduce the temperature to 325°F (165°C) and continue roasting until the beef reaches your desired doneness, about 45 to 75 minutes more depending on the size and shape of your roast. For a 3 to 4 pound roast, start checking the internal temperature after 45 minutes at the lower heat. Aim for about 125°F (52°C) for medium-rare, 135°F (57°C) for medium, measured with an instant-read thermometer inserted into the thickest part of the meat.
Once the roast reaches your preferred temperature, remove it from the oven and tent it loosely with foil right on the baking sheet. Let it rest for at least 15 to 20 minutes. The juices will settle back into the meat, and the internal temperature will rise another 5 to 10 degrees while the mustard crust sets.
After resting, transfer the roast to a cutting board. Using a sharp carving knife, slice the beef thinly against the grain so each piece is tender and shows off that juicy pink center under the golden mustard crust.
Arrange the slices on a warm platter, spoon any pan juices from the foil over the top or into a small pitcher, and bring it straight to the table for a Sunday dinner that looks every bit the showstopper Earl promised.