Preheat the oven to 375 degrees F. In a mixer fitted with a whisk attachment (or using a hand mixer), whip the egg whites until foamy. Add the cream of tartar and salt and continue whipping until soft peaks form. With the mixer running, gradually add 1 cup of the sugar and continue whipping until stiff and the sugar has dissolved, about 30 seconds. Sift the remaining 1/2-cup sugar with the pre-sifted cake flour 3 times, to aerate the mixture. Fold into the egg whites, then fold in the vanilla, zest, and cranberries. Spoon the batter into an ungreased tube pan. Bake until light golden brown, 30 to 35 minutes. Cool by hanging the cake (in the pan) upside down around the neck of a bottle until it cools to room temperature. Run a long, sharp knife blade around the cake to loosen, then knock the cake out onto a plate. The outside of the cake will remain in the pan.
Glaze: Stir the ingredients together until smooth.
Pour glaze over the top of the cake and spread with a spatula, letting it trickle down the sides. Let set for at least 30 minutes before serving, or until the icing is hard. Cut with a serrated knife, using a sawing motion.
Recipe courtesy of Gale Gand, ?Butter Sugar Flour Eggs? by Gale Gand, Rick Tramonto, Julia Moskin: Clarkson N. Potter Publishers, 1999