Originally Posted by Mdboatbum
Agreed, pull it at 120˚. It'll coast to probably 125˚-127˚. Rather than heating in the oven, which runs the risk of overcooking the whole thing, they could slice and heat on a grill or in a hot skillet. Or they could use the old restaurant standby of a dip in simmering Au-jus to bring to temp. About a minute will warm it to mid rare, and 2 minutes will satisfy even the most ardent fans of well done meat, while not actually overcooking or drying out the meat.
Slicing and heating on a grill/skillet, or steeping in Au Jus will work in a pinch, but both methods change the texture and/or flavor profile of the PR to some degree. Steeping in Au Jus will bring it up to temp, but you'll lose that remarkable edge to edge color/flavor as the exposed faces of the slices will brown. Heating on a grill/skillet will also cook the PR up, losing the edge to edge color, and it will also sear the PR giving it a slightly different flavor.
Neither of these are "bad", just distinctly different. I mean, if I ordered a PR in a restaurant and they sent out a cut that had been grilled, I'd send it back as that isn't what I ordered. If I had wanted it that way, I'd have asked for it to be done, or I would have just ordered a Ribeye.
FTR, when I cook a PR to just under mid rare, I do use the steeping method for people who want their PR cooked up to medium, mid-well or well. I also steep in Au Jus when I'm reheating a leftover slice for myself afterwards, but as it's "leftovers" at that point, I accept the sacrifice in taste.
All that said, it's personal preference. Some people actually prefer to have their PR grilled after it's been roasted and sliced :)
Also: If you do steep in Au Jus, make sure that the Au Jus isn't close to boiling. If it's too hot, the PR will basically par boil, which will also change the texture/flavor profile