For the Rum Syrup:
For the Glaze:
Heat oven to 180°C.
In a large bowl, cream together butter and sugar until light and fluffy. Beat in the eggs one at a time and mix until well blended.
In a separate bowl, combine flour, and baking soda and add to the butter-sugar-egg mixture, blending well.
Add the buttermilk and the vanilla extract, incorporate completely.
Bake for 1 hour or until toothpick tests clean. Cool on wire rack for 20 minutes, then invert.
Meanwhile, make the Rum Syrup by placing sugar, water, and zests in a small saucepan over high heat stirring constantly until the sugar is dissolved (about 5 minutes).
Strain the syrup into a 4-cup glass measuring cup and allow to cool. When cool, add the vanilla and rum, set aside.
While the cake is still warm, poke holes all over it and slowly pour some of the Rum Syrup over, letting it seep into the cake.
When it has been absorbed, pour more syrup over. You might have to do this two or three times.
While the cake is absorbing the Rum Syrup, make the Glaze by melting 2/3 cup sugar, 1/4 cup butter and orange juice in a small saucepan over medium heat
until the sugar dissolves.
Set the cake over a cooling rack and pour the Glaze over cake, letting it drip down the sides. Allow to harden.