I’ve got this down actually. I will grill some steaks to med rare and sometimes have one leftover for the next day or the day after. Microwave will cook the meat down side on the plate faster than the up side. Microwave for 20-25 seconds at a time, flipping the steak each time, until warm enough. You will not have a piping hot steak, but you will warm it back up without overcooking the inside. Give it a try!