The basic method is:
- get the grill up to a high temperature (500-700F for me on the KJ);
sear for around 1-2 minutes on each side;
seal the grill & let the meat cook for between 20 & 40 minutes in the residual heat. I'm using a Kamado Joe, so I am still seeing around 400F when I take it off & somewhere around 30 minutes is giving us just over rare.
Let it rest for 20 minutes or so in foil & wrapped in a tea-towel.
I am still experimenting with this technique a little - sometimes I am having to put the beef back on the heat for a bit as it is coming out a little too under for our tastes. But once done you get the wonderful charcoal-grilled outer half a cm or so - which also then gets a good smoking once the grill is sealed up for the residual heat cook. The inside is really moist & tender as the final photograph shows.
Last night's meat was left on for 1 to 2 minutes each side at between 500 & 600F & then 20 minutes in the residual heat. This was too rare for us (actually it was blue in the middle!) so we put it back on for another 10 minutes in the residual heat. This gave us a perfect rare meat to our tastes. Not all of the fat rendered on the main fat side of the meat, so in hindsight I think I would have given it a little longer on the high heat just on that side. But to be honest that would just be for additional flavour as I don't eat the fat.
Some pictures from last night's grill: