I’m gonna plug the microwave on lowest power level again (link goes to my explanation starting at the word “Edit”, possibly wrong, for why this works well without damaging the food).
I’ve done this with inch-thick slabs of medium rare rib roast, and 12-14 minutes (time will depend on power output of your microwave) gets it to 125° with no change in color or “cooked-ness”.
Other than that, putting it in a bag in a big tub of water as @Meekah suggested is my second choice
Here’s a photo of piece heated to 125 in the microwave that I posted years ago on CH.
Edit - I had not read @BeefeaterRocks comment but it’s a very similar technique.
