Here's how to reheat red meats like standing rib, steak, eye of round or flank steak so you don't lose taste or quality.
For oven reheating, remember these mantras:
... the larger the piece of meat, the lower the heat and the longer the time
... the smaller the piece of meat, the higher the heat and the shorter the time.
For a two pound piece of red meat, pre-heat the oven to 350 degrees, put the meat into an oven-proof (duh) dish, cover with aluminum foil and place in the oven. After ten minutes, flip the meat and give it another ten minutes, removing the foil for the last five. ***Since I cook meat to "rare", this would give you a medium-rare result.
For stovetop reheating (this is actually best for smaller pieces of meat.)
Place a pan on the burner, bring to high heat, add a tablespoon of butter or oil. Then "fry" the meat for about 2-5 minutes a side (depending on thickness). For a flavorful jus, deglaze with 1/2 cup of red or white wine and reduce by half. Then turn the heat off, add two tablespoons of very cold butter, and swirl in. You'll love me for this.
Note: If you prefer rare meat, use the broiler of your oven. It will give you intense heat from above, searing the outer layer and protecting the inside. Place the meat on a slightly greased sheet pan and place under the broiler for two minutes. Flip and continue for another 3-4 minutes. Let the meat rest three minutes before eating. This is best for pieces one to two inches thick... the center will be warm instead of hot, which is as it should be.
For microwave re-heating: DON'T DO IT! (unless you love rubber)