The finesse factor -- that "magic touch" that cooks who can turn the ordinary into the extraordinary seem to have -- really shines when cooking the basics, such as a roast chicken or classic roast beef and potatoes. There's no secret to cooking a tender roast beef with potatoes and onions. You just have to get a good sear on the meat using dry heat, then tenderize it with moist heat. The onions and potatoes take care of themselves when you cook the roast, so you can pop the whole thing in the oven at once and turn something simple into something elegant -- finesse in its purest form.
Remove the roast from the refrigerator and let it reach room temperature. If thawing a frozen roast, place it in a shallow pan lined with paper towels and place it on the bottom shelf of the fridge. Allow about 2 hours of thawing for every pound of beef.
Place an oven rack in the middle position of the oven and remove any other trays or racks. Heat the oven to 400 degrees Fahrenheit and turn the fan on, if using a convection oven.
Place the roast on a cutting board and remove any loose, hanging pieces of fat from it using a kitchen knife. Also remove any 1- to 2-inch-thick layers of surface fat, referred to as fat caps, from the roast.
Rinse 4 or 5 new potatoes and peel 1 or 2 onions for every pound of roast and place them on a cutting board. Cut new potatoes larger in diameter than a walnut in half. Cut the onions in quarters or halves with a kitchen knife so they're roughly the size of the potatoes.
Spread the potatoes and onions in an even layer on a wire rack set over a pan that measures at least 3 inches deep. You can use an aluminum roasting pan if you don't have a drip pan. Drizzle the potatoes and onions liberally with vegetable oil or regular olive oil.
Season the potatoes to taste, or follow a guideline of 1/2 teaspoon of kosher salt and 1/4 teaspoon of freshly ground black pepper for every 5 potatoes. Place the roast on top of the vegetables.
Drizzle vegetable oil or regular olive oil over the roast and season it to taste. If you're unsure of how to season it, keep it simple. Use about 1/2 tablespoon of kosher salt and 1/4 tablespoon of freshly ground black pepper per pound. Rub the seasoning and oil all over the outside of the roast.
Place the roast and veggies in the oven and cook until the outside of the beef develops a golden-brown color, or the color you want it at when you remove it after cooking. You'll lower the temperature and cook the roast in moist heat after you sear it, so the roast won't get darker on the outside during cooking. You get a good sear on a roast after about 12 to 15 minutes in an oven set to 400 F.
Lower the heat to 300 F after your sear the roast. Open the door and pull the rack out so you have access to the roast without removing it from the oven.
Pour about 2 inches of liquid through the rack the roast sits on and into the pan underneath it. The liquid creates steam during cooking, so you can use just about any liquid. Water, wine, beer and stock all work with a beef roast.
Cover the roast and veg with a large piece of aluminum foil and mold it around the edges of the pan to seal it. Wear oven mitts when covering the pan with aluminum foil, which lets the moist heat rising from the pan of liquid underneath to collect around the roast.
Check the temperature of the roast after 30 minutes of cooking with a meat thermometer. Insert thermometer in the center of the roast as deep as you can when checking. Medium-rare, which takes about 30 to 40 minutes depending on the oven, measures about 130 F. Medium, which takes about 40 to 50 minutes, measures around 150 F. Well-done, which takes about 1 to 1 1/2 hours, measures about 160 F.
Open the oven door and pull the rack the roast sits on all the way out. Remove the pan and place it on a waiting cooling rack or cooling pad. Remove a corner of the foil from the pan to let the steam out, and let the roast sit for about 10 minutes before cutting into it.