Put your steak in the smoker, and let it smoke until the internal temperature is 100 degrees. If you're working with a thicker cut of meat - 2" plus in thickness - you'll want to take the internal temperature up to 125 degrees.
When your steak gets to the target internal temperature, pull it off the grill and tent it with foil, and turn up the temperature of your smoker to 400 degrees. If you have a cast iron skillet, put it in the smoker while it's warming up.
Right before you put your steak in the skillet, add a tablespoon of butter.
Once the smoker is at 400, put your steak back in. After 3 minutes flip the steak, and let it cook for an additional 3 minutes. Pull it from the smoker after the 6 minutes of total sear time and wrap it tightly with foil.
Let your steak rest for at least five minutes. If its a thicker cut of meat you can let it rest for up to 20 minutes.