In a small bowl, mix flour, cocoa, baking soda, baking powder, and cinnamon. In a large bowl, beat egg whites, brown sugar, yogurt, vanilla, and almond extract until well blended. Stir in flour mixture and beat just until evenly moistened.
Pour batter into an 8-inch-square nonstick (or greased regular) baking pan. Bake in a 350-degree F oven until center of cake springs back when lightly pressed (30 to 40 minutes). Let cake cool in pan on a rack for 15 minutes; then invert it onto a serving plate. Serve warm or cool. If made ahead, wrap cooled cake airtight and store in a cool place until next day (freeze for longer storage).
Just before serving, sift powdered sugar over cake. To serve, cut cake into wedges or rectangles. If desired, sift more powdered sugar over each serving; then top with Spiced Cream, if desired.