Grilled Butterflied Leg of Lamb with Rosemary Sea Salt & Charred Lemons

Preparation

1. In a food processor, grind the salt and 1/4 cup rosemary leaves together until the mixture is the texture of coarse sand. The rosemary salt can be used immediately, or dried for later use. To dry, spread the salt mixture on a large plate and leave it out at room temperature, uncovered, until fully dried, about 1 day. Store in a sealed container; it will keep for several months. 
2. Season the butterflied leg of lamb generously with the rosemary salt or Jacobsen Rosemary Salt, working it into all the crevasses; it should take about 2 tablespoons. Set the lamb aside at room temperature for at least 30 minutes before grilling, or cover and refrigerate for up to 2 days.
3. Prepare a hot fire in a charcoal or gas grill. Pat the lamb dry, if needed, and rub it lightly with olive oil to coat.
4. Grease the grill grates with oil, and place the lamb on the hottest part of the grill. Cook with the grill covered, turning once, until brown and crusty all over. Move the lamb to a cooler part of the grill, and continue cooking until an instant-read thermometer inserted into the center registers 130°F for medium rare, 15 to 25 minutes total. (Carry-over cooking will increase the internal temperature off the grill.) 
5. Transfer the lamb to a platter, cover with foil, and let it rest at least 10 minutes before cutting it into thick slices against the grain.
6. Meanwhile, halve the lemons and brush the cut sides lightly with oil. Place them cut side down on the grill until deeply charred, 2 to 3 minutes.
7. Arrange the lamb slices on a large platter. Serve with the charred lemon halves for squeezing, and more of the rosemary salt.