Chocolate Angel Food Cake

1/4 cup unsweetened cocoa powder,
1/4 cup hot, strong coffee
3/4 cup sifted cake flour
1 1/4 cups sugar, divided
1/4 teaspoon salt
12 large egg whites, at room temperature (see Tip)
1 teaspoon cream of tartar

Preheat oven to 350°F.

Dissolve cocoa in coffee in a medium bowl; let cool to room temperature. Combine 1/2 cup sugar, flour and salt in a small bowl.

Beat egg whites with an electric mixer in a large bowl until frothy. Add cream of tartar and continue beating until soft peaks form. Gradually add the remaining 3/4 cup sugar and beat just until stiff peaks form. Do not overbeat.

Sift the flour mixture over the beaten egg whites in 3 parts, folding in gently after each sifting. Stir approximately 1 cup of the egg-white mixture into the coffee mixture. Fold it back into the egg-white mixture until thoroughly combined. Pour the batter into an ungreased 10-inch tube pan. Smooth the top and run a small knife or spatula through the batter to remove any air pockets.

Bake until a cake tester comes out clean and the top springs back when touched lightly, 50 to 60 minutes. Invert the pan over the neck of a bottle and let cool completely. With a knife, loosen the edges and invert the cake onto a serving platter.