In a medium saucepan over medium heat, combine sugar, orange juice, butter, cinnamon stick, bourbon if using, nutmeg, and salt.
Stir to combine and bring to a boil, then reduce to a simmer and cook until it has thickened slightly, about 10 minutes. When reduced, remove and discard cinnamon stick.
Meanwhile, prep potatoes: Peel potatoes and slice into 1/2″ rounds, then layer in prepared baking dish. Pour thickened syrup over potatoes and cover dish with aluminum foil.
Bake 30 minutes, then remove foil and bake about 50 minutes to 1 hour more, basting with sauce every 15 minutes.
Let cool slightly before serving.