Prepare Vanilla Pastry Cream.
Preheat oven to 350°.
Coat bottom of a 9-inch round cake pan with cooking spray. Dust with 2 teaspoons flour; set aside.
Beat 1/2 cup sugar and margarine in a medium bowl at medium speed of a mixer until well-blended (about 5 minutes). Add vanilla and egg yolk, and beat well. Sift together 1 1/2 cups flour, baking powder, and salt. Add flour mixture to creamed mixture alternately with milk, beginning and ending with flour mixture.
Beat egg whites at high speed of a mixer until foamy using clean dry beaters. Gradually add 3 tablespoons sugar, beating mixture until stiff peaks form. Gently stir one-fourth of egg white mixture into batter. Gently fold in remaining egg white mixture. Pour into prepared pan. Bake at 350° for 35 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on a wire rack; remove from pan. Cool completely on wire rack.
Split cake in half horizontally using a serrated knife; place bottom layer, cut side up, on a serving plate. Spread Vanilla Pastry Cream evenly over bottom layer; top with remaining cake layer. Spread Chocolate Glaze evenly over top. Chill 1 hour or until glaze is set.