Preheat oven to 325 degrees. Beat egg yolks at high speed 5 minutes. Add condensed milk, beat at low speed 1 minute. Add cream of tartar, then lime juice. Beat until smooth. Spoon into crust. Bake 15 minutes or until set. Cool to room temperature. Refrigerate at least 6 hours.
Preheat oven to 500 degrees.
Meringue: Heat egg whites in a double boiler with the 4 tablespoons sugar, stirring frequently to 110 degrees. Beat at high speed until stiff peaks. Spread over filling, sealing to crust. Bake at 500 degrees for 3-5 minutes or until nicely browned. Chill at least 2 hours.
