I just love local domestic lamb; it's amazing and flavorful and, I think, the best in the world. Although many favor New Zealand lamb, I love the fact that American-raised lamb is allowed to graze on pasture, not in inhumane feed lots. Lamb has a complex yet sweet flavor that takes very well to strong spices such as ancho chile, coriander, and cumin. I learned how to balance the flavors of chiles with their natural heat while working with Bobby Flay at Mesa Grill in the early 1990s. Ancho chile is a particular favorite of mine: It is mildly hot with a wonderful raisin-ated, sun-dried quality, as well as a gorgeous russet color.
In a small bowl, mix together the olive oil, cumin, coriander, chile powder, lemon zest and juice, garlic, and rosemary to form a paste.
Place the lamb in a shallow dish or baking sheet and smear the marinade all over both sides.
Cover with plastic wrap and marinate in the refrigerator for at least 2 hours, or up to 4 hours. (Don’t let marinate too long or the acid might start to cook the meat and change the texture.)
Remove the lamb from the refrigerator and let come to room temperature. If using a grill pan and the cut is too large for your pan, cut up into segments.
Prepare a grill: Prepare a gas grill for medium-high heat, prepare a charcoal grill with a
Season the lamb with salt and pepper and drizzle with olive oil. Grill over medium-high heat or the hot zone of the charcoal fire, turning once, for 10 minutes per side.
Turn down the heat or move the lamb to the cool zone, and continue grilling, turning once or twice, until an instant-read thermometer inserted in the thickest part of the lamb registers 138° to 142°F for medium, about 15 minutes longer.
(If your grill is too hot, and the lamb begins to char, you can use your oven as a backup: Transfer to a 400°F oven to finish cooking.)
Carve the lamb across the grain into very thin slices.