Preheat oven to 400°. Heat a sauté pan over medium-high heat. Season meat with salt and five-spice powder. Sear the lamb on both sides and place in oven for 15 to 20 minutes for a medium-rare temperature. Season the pineapple with cinnamon, salt, pepper, and brown sugar and roast in the oven with the lamb. Cook until nice and golden brown. When the lamb is finished, let it rest.