Heat oven to 350°F. In large bowl, combine egg whites and cream of tartar; beat until soft peaks form. Gradually add 3/4 cup of the sugar, beating at high speed until stiff peaks form.
In small bowl, combine egg yolks, remaining 3/4 cup sugar, flour, orange peel, baking powder, salt, nectar and rum extract; beat at low speed until moistened. Beat 1 minute at medium speed. Pour over egg white mixture; fold in gently just until blended. Pour batter into ungreased 10-inch tube pan.
Bake at 350°F. for 35 to 45 minutes or until top springs back when lightly touched. Immediately invert cake onto funnel or soft drink bottle; let hang 1 hour or until completely cooled. To remove cake from pan, run edge of knife around outer edge of pan and tube.