How to Make It
Preheat oven to 325°.
Lightly spoon sifted flour into a dry measuring cup; level with a knife. Sift flour again into a small bowl; add 3/4 cup sugar and rind, stirring mixture well with a whisk.
Place egg whites in a large bowl; beat with a mixer at high speed until foamy. Add cream of tartar and salt; beat until soft peaks form. Gradually add remaining 3/4 cup sugar, 1 tablespoon at a time, beating until stiff peaks form. Beat in lemon extract and lime juice. Sift 1/4 cup flour mixture over egg white mixture; gently fold in. Repeat procedure with remaining flour mixture, 1/4 cup at a time.
Spoon batter into an ungreased 10-inch tube pan, spreading evenly. Break air pockets by cutting through batter with a knife. Bake at 325° for 55 minutes or until cake springs back when lightly touched. Remove cake from the oven. Invert pan; cool completely. Loosen cake from sides of pan using a narrow metal spatula. Invert cake onto a plate.