Grilled Butterflied Leg of American Lamb with Rosemary Sea Salt and Charred Lemons

In a food processor, grind salt and 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 salt mixture on a large plate; leave it out at room temperature, uncovered, until fully dried, about 1 day. Store in a sealed container; it will keep for several months. (This is great to have on hand to season any cut of lamb!) 

Season lamb generously with rosemary salt or Jacobsen Rosemary Salt, working it into all crevasses; it should take about 2 tablespoons. Set lamb aside at room temperature for at least 30 minutes before grilling, or cover and refrigerate for up to 2 days. 

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. 

Grease grill grates with oil; place lamb on the hottest part of the grill. Cook lamb with grill covered, turning once, until brown and crusty all over. Move lamb to a cooler part of the grill; 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.) Transfer lamb to a platter; cover with foil, and let it rest at least 10 minutes before cutting it into thick slices against the grain. 

Meanwhile, halve the lemons; brush the cut sides lightly with oil. Place cut side down on the grill until deeply charred, 2 to 3 minutes. 

Arrange lamb slices on a large platter or directly over a salad. Serve with the charred lemon halves for squeezing, and more rosemary salt.