Step 1

Preheat oven to 425°F.

Step 2

If your beef is in the refrigerator, take it out and set it on the counter to come to room temperature for 10 minutes.

Step 3

In a medium bowl, mix together olive oil, garlic, rosemary, salt, and pepper.

Step 4

In a separate large bowl, add the halved/quartered red potatoes. Pour half of the olive oil mixture over potatoes and toss to coat.

Step 5

Rub the remaining half of the olive oil mixture over all sides of the roast.

Step 6

Place the sliced onions in a cast iron pan, then place roast on top of the onions in the pan. Spread potatoes around the roast in the pan.

Step 7

Place pan in the middle rack of your oven, and bake at 425°F for one hour.

Step 8

At one hour check for doneness. Meat is ready when an internal thermometer reads 145°F (for medium). If meat is not cooked fully at one hour, keep it in the oven and check for doneness with a thermometer every 10 minutes.

Step 9

Allow the meat to rest, covered in foil, at room temperature for 15 minutes before slicing and serving.