Preheat oven to 350 degrees.
Sift powdered sugar, flour, cocoa, and cinnamon together 3 times.
Set aside.
In a large mixing bowl combine egg whites, cream of tartar, and vanilla.
Beat on medium speed until soft peaks form.
Gradually add sugar, about 2 tablespoons at a time, beating on high speed until stiff peaks form.
Sift about 1/4 of the dry mixture over beaten egg whites; fold in gently.
Repeat, foldng in the remaining dry mixture by fourths.
Pour into an ungreased 10 inch tube pan.
Using a narrow metal spatula or knife, gently cut through the batter to eliminate air bubbles.
Bake on the lowest rack for 40 - 45 minutes or until top springs back when lightly touched.
Immediately invert cake in pan onto bottle.
Cool completely.
Loosen side of cake from pan; remove cake.
Serve cake drizzled with chocolate syrup.