Heat the oven to 350 degrees. Grease and flour two 8 ½ x 4 ½ x 2 ½-inch loaf pans. Line the bottoms with parchment paper.
Cream the butter and 2 cups of the granulated sugar in the bowl of an electric mixer fitted with the paddle attachment for about 5 minutes, or until light and fluffy.
With the mixer on medium speed, beat in the eggs, one at a time, and the orange zest.
In a large bowl, sift together the flour, baking powder, baking soda, and salt.
In another bowl, combine ¼ cup of the orange juice, the buttermilk, and vanilla.
Add the flour and buttermilk mixtures alternately to the batter, beginning and ending with the flour.
Divide the batter evenly between the pans, smooth the tops, and bake for 45 minutes to 1 hour, until a cake tester comes out clean.
While the cakes bake, cook the remaining ½ cup of granulated sugar with the remaining ½ cup orange juice in a small saucepan over low heat until the sugar dissolves.
When the cakes are done, let them cool for 10 minutes. Take them out of the pans and place them on a baking rack set over a tray. Spoon the orange syrup over the cakes while they're still warm. This will allow the cakes to absorb the syrup better. Then allow the cakes to cool completely.
Frosting Glaze: Combine the confectioners' sugar and orange juice in a bowl, mixing with a wire whisk until smooth. Add a few more drops of juice, if necessary, to make it pour easily. Pour over the top of the cakes and allow the glaze to dry. Wrap well, and store in the refrigerator.
Sugared Cranberries: Combine ½ cup sugar and ½ cup water in a sauce pan. Cook over medium heat until sugar is dissolved, about 2 - 3 minutes. Stir in cranberries until they're coated well with the syrup.Using a slotted spoon, transfer the cranberries to a wire rack over a sheet pan. Let dry for at least 1 hour. Working in batches, roll the sticky cranberries in the remaining sugar until well coated. Place them back on the wire rack and let dry for at least 1 hour.