1) Buy a meat thermometer, and get an oven thermometer to place in oven;
2) Pre-heat oven to desired temp of steak (130° F / 54 ° C is medium rare);
3) Room temp steak, season aggressively with salt;
4) Heat pan as hot as it will get, add a bit of either groundnut (peanut) oil or safflower oil to the pan;
5) Add steak, sear for 60 seconds per side, remove from pan;
6) Place steak on sheet tray or other device, put in oven, cook for about 90 mins - 2 hrs, check internal temp, remove when desired temp is achieved;
7) Refresh sear, with a bit of melted butter and thyme (maybe garlic, too);
You can replace the oven with your kitchen sink full of 130° F / 54 ° C water; it will hold that temp for a surprisingly long period of time, perhaps 35-40 minutes depending on the material and the relative size of the steak. Just refresh with hot tap water to maintain the temp. Place seared steak in a Ziploc with some fat (EVOO or butter) and some thyme, lower Ziplock into the water until you get to the level of the zippy bit (this will force all the air out), then seal the bag and drop it into the water bath. If you do this, just remember that each steak you cook gets its own bag, and you'll want to be sure to cool the steaks down to room temp before bagging. With this method, you can pre-cook everything and store in the oxygen-free sealed bag for probably close to a week in the fridge prior to the day you want to eat them, or in the freezer for a couple months. Just temper back to room temp and refresh the sear.
These methods work flawlessly because the cooking medium is the temperature you want for the finished product.... which means, you simply cannot overcook your steak. When I use this method for steak, I actually do a two-rib roast and leave it in a 125° / 52° C oven for 24 hours, then portion it into steaks and sear. I also sear using a propane torch.
I like cooking.