Note Cedro is the fruit of the citron tree. Glacé cedro is available from select delicatessens, Simon Johnson and David Jones food halls. If it's unavailable, substitute candied orange peel or candied lemon peel. If you plan to make the cakes well in advance, you'll need to "feed" them with rum to keep them moist. Once a week, unwrap cakes and drizzle each with a tablespoon of rum, then re-wrap. Ice them just before serving.