For the lamb, set lamb onto a large work surface. Cut a long piece of butchers twine; set both aside.
Combine 4 teaspoons (20ml) olive oil with garlic, shallot, parsley, rosemary, thyme, oregano and lemon zest in a small bowl. Season the inside and outside of the lamb with salt and pepper. Spread oil mixture over inside of the lamb. Roll the loin into the tenderloin and rib apron, then tie the roast with twine. Set aside to marinate for 10 minutes.
Preheat oven to 350F (175C).
Set a cast iron or stainless-steel skillet over medium-high heat. Rub the outside of the roast with remaining 2 teaspoons (10ml) of olive oil. Add the roast to the pan and sear until well-browned all over, about 10 minutes.
Transfer the skillet to oven and roast until the internal temperature reaches 125F (52C), about 15 to 20 minutes. Transfer onto a cutting board and tent with aluminum foil. Rest for 10 to 15 minutes before slicing.
For the gremolata, whisk together lemon zest and juice, garlic, parsley, oregano, Dijon and olive oil in a small bowl. Season with salt and pepper. Serve with lamb.