Preheat oven to 325. Grease a 9x5x3-inch loaf pan.
Put orange juice in a 1-cup measure. Add enough boiling water to orange juice to make 3/4 cup. Add grated orange peel and butter; stir until butter is melted. Set aside.
In a mixing bowl, beat sugar & egg together; add orange mixture and stir until well blended. Add cranberries (and walnuts, if using them).
In a separate bowl, sift together flour, salt, baking powder, and baking soda. Stir into the egg and orange mixture. Pour batter into a greased loaf pan. Bake for about 1 hour, or until a toothpick inserted into center of loaf comes out clean.
Cool on a rack and store overnight before serving.