Beat the egg yolks until thick and lemon colored, then add
     the sugar gradually, beating as you add.  Continue to beat
     until the mixture is thick and puffing with air.  Add the lemon
     juice and rind, and orange juice.  Mix together the cake 
     meal, potato starch, and salt; fold lightly into the egg yolk 
     mixture.  Beat the egg whites until they stand in peaks, but 
     stop beating before they look dry and shiny.  Fold into the 
     cake batter.  Line bottom of a regular cake pan (about 8" x 14" 
     or 9" x 13") with wax paper; pour in the batter.  Bake in a slow 
     oven (325 degrees) for one hour, or until baked through. 

     Serve topped with powdered sugar or sugared berries.

     Serves 24