It may strike you as curious, but adding an entire orange to this easy snacking cake, rind and all, imparts a wonderful flavor reminiscent of orange marmalade, pleasantly bitter and sweet. A high-speed blender is the best way to process the orange, but a food processor works too. You want the purée to be as smooth as possible. While the cake bakes, prepare an easy orange glaze. For that step — or any recipe requiring both orange zest and juice — be sure to zest your orange before juicing it, as it’s much more difficult the other way around.