I saw a chef use an interesting trick to re-heat slabs of prime rib. Put the meat on a sizzle platter or oven-proof tray of some sort, and place one of the leaves from the outside of a head of iceberg lettuce on top of the meat, pressing so it sticks to the meat. Re-heat in a 300 degree oven just until warmed. The inside of the meat remains red.
set up a makeshift sous-vide station in your kitchen sink. *seal* the meat completely in a plastic bag, submerge it in a bowl or pot of 130 or 140-degree water, weigh it down with something to keep in completely submerged, and add more hot water every few minutes as it cools down to keep the temperature relatively constant. should take about 30 minutes to warm it all the way through without cooking it.