2 cups sugar divided
1 1/3 cups sifted cake flour (not self-rising)
1 1/2 cups egg whites, at room temperature (10 to 12 eggs)
3/4 teaspoon kosher salt
1 1/2 teaspoons cream of tartar
3/4 teaspoon pure vanilla extract
1 1/2 teaspoons grated orange zest (1 large orange)
1 cup confectioner's sugar
2-3 tablespoons fresh orange juice
1/4 teaspoon cinnamon
Preheat the oven to 350 degrees F.
Combine 1/2 cup of sugar with the flour and sift together 4 times, or pulse together in a food processor. Set aside.
Place the egg whites, salt, and cream of tartar in the bowl of an electric mixer fitted with a whisk attachment and beat on high speed until the eggs make medium-firm peaks, about 1 minute. With the mixer on medium speed, add the remaining 1 1/2 cups of sugar by sprinkling it over the beaten egg whites in a constant stream. Beat for a few minutes until thick and shiny. Beat in the vanilla and orange zest and continue to whisk until very thick, about 1 more minute. Sift about 1/4 of the flour and sugar mixture over the egg whites and fold it into the batter with a rubber spatula. Continue adding the flour by fourths by sifting and folding until all of the flour is incorporated.
Pour the batter into an ungreased 10-inch tube pan, smooth the top, and bake it for 40-45 minutes, until it springs back to the touch, and a toothpick inserted into the center comes clean. Remove the cake from the oven and invert the pan on a cooling rack until cool, 1- 1 1/2 hours. Unmold cake from pan and drizzle glaze over the top with the tines of a fork.
For the glaze:
Stir together the confectioner's sugar and orange juice together until you reach a drizzling consistency. Stir in the cinnamon, mix well, then pour over the top of the angel food cake.