1To make the cake, preheat the oven to 350. Butter a 10 inch tube pan; flour the pan, tapping out the excess and set aside.
2Onto a sheet of waxed paper, sift together the flour, baking powder, baking soda and salt. Toss in the coconut and set aside.
3In a large bowl cream the butter with an electric mixer on high speed until light. Gradually add the sugar and continue beating until the mixture is very light and fluffy. Change the mixer speed to medium. add the eggs, on at a time, beating well after each addition, then beat in the orange zest. The mixture may look curdled, but this is nothing to worry about.
4Change the mixer speed to low. Alternately beat in the sifted dry ingredients and the orange juice, beginning and ending with the dry ingredients and beating only until combined. Pour the batter into the prepared pan.
5Bake until the cake is golden brown on top and skewer inserted halfway between the sides and the tube of the pan comes out clean, about 1 hour and 25 minutes. Cool the cake in the pan on a wire rack for 15 minutes, then carefully invert the cake onto the rack and turn right side up.
6To make the orange glaze, beat together the glaze ingredients in a small bowl until smooth and well blended. Place the warm cake on a plate and spoon the glaze over it. Sprinkle with the toasted coconut, if desired. Let the cake cool completely before serving