Using a citrus zester, zest one of the oranges. Using a sharp knife, finely julienne the zest. Using a serrated knife, peel all the oranges, removing all of the bitter white pith. Working over a bowl, cut in between the membranes to release the sections into the bowl. Squeeze the membranes to extract as much juice as possible; you should have about 1 cup.
In a medium saucepan, melt the butter. Add the onion and cook over moderately high heat, stirring, until softened and lightly browned, about 8 minutes. Add the honey and cook until lightly caramelized, about 3 minutes. Add the orange zest, sections and juice and bring to a boil. Reduce the heat to low and simmer until the liquid is reduced to a syrup and the sections have nearly broken down, about 30 minutes.