Preheat oven to 350 degrees F.
Butter and flour two 9x5 loaf pans and set aside.
In a large bowl, add the sugar and orange zest and stir well to combine. Then add the flour, salt, and baking powder, stir again, and set aside.
In a medium mixing bowl, combine the eggs, buttermilk, melted butter, orange juice, and vanilla. Whisk well to combine.
Slowly add the wet ingredients to the bowl with the dry ingredients, stirring until well combined.
Add the cranberries to the batter and fold them in.
Pour the batter into the two prepared loaf pans.
Bake in a convection oven for 45-60 minutes, or until a toothpick inserted in the center comes out clean. In a non-convection oven, it could take 60-70 minutes. If the loaf begins to look too brown, loosely cover it with parchment paper until it is cooked through.
Once cooked through, remove the loaf pans from the oven and let cool for 10-15 minutes. Using a butterknife, loosen the sides. Place a platter on top of the loaf pan and flip it over to release the loaf from the pan. Let cool before glazing.
Glazing: In a small bowl, combine the powdered sugar, orange zest, and 1 tablespoon of orange juice and mix. If the glaze is too thick, add a touch more orange juice. The glaze should be the consistency of batter, thick but spreadable.