Place oven rack in lowest position. Heat oven to 350°F.
Sift flour and cocoa into a bowl. Add espresso and cinnamon.
Beat egg whites in medium-size bowl until frothy. Beat in cream of tartar. Beat in sugar, 2 tablespoons at a time, until soft, glossy peaks form.
Fold flour mixture, in thirds, into whites. Spoon batter into ungreased 10-inch tube pan; smooth surface.
Bake on bottom rack in 350°F oven for 45 minutes or until top is dry and cracked. Invert cake pan and slip center tube over top of bottle so pan is elevated. Let cool 1 hour. Remove cake from pan. Drizzle with chocolate.