Preheat the oven to 375 degrees. In a large mixing bowl, combine flours, baking soda and salt. Set aside. In another bowl, cream butter and sugar until light and fluffy. Add eggs, buttermilk and zest. Make a well in the center of the dry ingredients and pour in the liquid ingredients. Stir to almost combine, but do not overmix. Optionally, fold in diced orange sections and dried cranberries.

Spoon batter into a well buttered muffin tin about 2/3 rds full. Bake for 25 minutes or until toothpick comes out clean. Brush hot muffins with orange juice and sprinkle with sugar. Leave muffins in tins for 10 minutes before moving to a wire cake rack to cool.