In a blender, puree the oil, onion, garlic, dill, lemon juice, enthusiasm and oregano. In a baking dish, put the marinade over the lamb and turn to coat. Refrigerate for a minimum of 4 hours. Remove from the fridge 1 hour prior to cooking. Light a grill. Remove the marinade and season the lamb with salt and pepper. Grill over moderate heat for 28 minutes, turning as soon as, until medium-rare. Transfer to a surface area and let rest for 10 minutes. Slice the lamb against the grain and serve.