Beat egg whites until frothy; add cream of tartar and beat at high speed until soft peaks form. Gradually add ¾ cup sugar; continue beating until stiff but not dry. Set aside. Beat yolks about 3 minutes or until very thick and light in color. Add remaining sugar 1 tablespoon at a time; beat until thick. Add orange juice and peel; blend until smooth. Thoroughly combine flour, finely chopped pistachios and salt; gently fold into egg yolk mixture until well-blended. Fold yolk mixture into beaten whites. Pour into 6 (5 ¾ x 3 ¼ x 2 ¼ inch) ungreased pans; cut through batter with spatula to remove air bubbles. Bake at 325° F. 25 to 35 minutes or until cakes spring back when lightly touched. Immediately invert pans on wire racks; cool completely. To remove cakes, loosen around edges of pans with knife. Pour Orange Syrup over cakes; allow to sit until syrup is absorbed. Garnish tops of cakes with chopped pistachios.