Cream butter and shortening in a large mixing bowl; gradually add 1 cup sugar, beating until light and fluffy. Add 2 eggs, one at a time, beating well after each addition. Stir in orange rind. Gradually add flour, stirring well after each addition. Chill 1 hour.
Shape into 1-inch balls; roll each ball into a 6-inch rope. Tie each rope into a knot, leaving 1/2- inch ends. Place 2 inches apart on ungreased cookie sheets; set aside.
Beat egg white (at room temperature) until soft peaks form. Gradually add remaining sugar, 1 tablespoon at a time, beating until stiff peaks form. (Do not under beat.)
Brush meringue over cookies. Bake at 375° for 8 to 10 minutes. Remove from cookie sheets, and cool on wire racks.