Sift together flour, cocoa powder, 1/4 cup sugar and cinnamon into a bowl; set aside.

With an electric mixer, beat egg whites, cream of tartar, warm water, vanilla and salt in a large bowl at high speed until foamy. Gradually add remaining 1 cup sugar, 2 tablespoons at a time, beating until stiff peaks form. Sift flour mixture over egg white mixture, 1/4 cup at a time; fold flour mixture in gently.

Spoon batter into an ungreased 10-inch tube pan, spreading evenly. Break air pockets by cutting through batter with a knife. Bake for 45 minutes or until cake springs back when lightly touched. Invert pan; let cool completely. Loosen cake from sides of pan using a narrow spatula; revert cake onto plate.