Let lamb sit at room temperature for about 30 minutes. Preheat oven to 450ºF.

If the lamb comes in netting, leave it on. If not, tie the roast in several places so it keeps its shape (or better yet, have your butcher do it). Rub with 1 tablespoon olive oil and season generously on all sides with salt and pepper. Roast the leg of lamb for 15 minutes. Reduce the oven temperature to 350ºF, then continue to roast for another 60-90 minutes or until the internal temperature reads 135ºF (for medium rare) on an instant-read thermometer. Remove from the oven, cover with foil, and let sit for 20-30 minutes before slicing.

In a food processor fitted with the steel blade or in a blender, combine the garlic cloves, mint, basil, pistachios, lemon juice and zest, ½ teaspoon salt, and ¼ teaspoon pepper. Blend to combine. With the machine running, add ½ cup olive oil and blend until smooth. Taste and add more salt and pepper if needed.

Spoon a little of the pesto on top of the lamb and serve the rest on the side.