Preheat the oven to 350°. Bring a large pot of salted water to a boil. In a large saucepan, heat the olive oil until shimmering. Add the lamb, onion, oregano, cinnamon, cloves and a generous pinch each of salt and pepper. Cook over high heat, stirring frequently, until the lamb is no longer pink and any liquid has evaporated, about 8 minutes. Add the marinara sauce and bring to a boil. Boil over high heat, stirring occasionally, until the sauce has reduced slightly, about 5 minutes.