Instead of searing the meat first on a hot pan and finishing it in the oven, you slowly bring the meat up to temperature in a low oven or smoker first, and then finish it with a quick, high-heat sear right before serving.

It's usually used for thick steaks or roast. But you don't do it for burgers because all the moisture escapes. Which it did here and then proceeded to be boiled and steamed since it was covered in tin foil