How to Make It
Preheat oven to 350°.
To prepare the cake, place the granulated sugar and butter in a large bowl, and beat with a mixer at high speed until well-blended. Add the egg, beating well. Combine cake flour, baking powder, and salt in a bowl, stirring well with a whisk. Add the flour mixture to the sugar mixture alternately with the milk, beginning and ending with flour mixture. Stir in rind and extract.
Beat the egg whites with a mixer at high speed until stiff peaks form using clean, dry beaters (do not overbeat). Fold egg whites into batter; pour batter into an 8 x 4-inch loaf pan coated with cooking spray. Bake at 350° for 50 minutes or until a wooden pick inserted in center comes out clean. Cool in pan for 10 minutes on a wire rack, and remove from pan. Cool completely on wire rack.
To prepare the glaze, combine the powdered sugar, liqueur, and juice in a small bowl. Poke holes in top of cake using a skewer; drizzle glaze over cake.