The secret to this rich and fudgy cake is good-quality unsweetened cocoa powder, which provides the smooth taste of chocolate without the fat.
Serves 6 to 8.
1 1/3 cups firmly packed golden brown sugar
1 teaspoon powdered sugar
Preheat oven to 350°F. Line bottom of 9-inch-diameter cake pan with 1 3/4-inch-high sides with waxed paper. Spray pan and paper with vegetable oil spray (or oil pan and paper lightly). Dust pan with flour; tap out excess.
Sift 1 cup flour, 1/3 cup plus 1 tablespoon cocoa, espresso powder, baking powder and baking soda into medium bowl. Using electric mixer, beat egg whites, brown sugar, yogurt and vanilla in large bowl until blended, about 1 minute. Mix in dry ingredients. Transfer batter to prepared pan.Bake cake until tester inserted into center comes out clean, about 35 minutes. Cool in pan on rack 15 minutes. Cut around pan sides to loosen cake. Turn out onto plate. Peel off paper and cool completely.
Combine remaining 1 tablespoon cocoa powder, powdered sugar and cinnamon in small bowl. Sprinkle over cake before serving.