I've been using this one for years:
9" baked graham cracker crust
For filling-
1/2 envelope gelatin
2 Tbl cold water
2 eggs, separated
1/2 C sugar
pinch or salt
juice of 1 lime and grated peel of 1/2 lime
1/2 C heavy cream, whipped until it holds a soft shape
-Make pie shell and cool. In a small saucepan, sprinkle gelatin over cold water and let stand 5 minutes or until spongy. Meanwhile, beat egg yolks with half the sugar, the salt, lime juice, and peel, until light and creamy. Pour into the top of a double boiler and cook, stirring, over gentle heat until mixture is the consistency of heavy cream. Take from heat. Dissolve gelatin over a pan of hot water and stir into lime mixture. Cool, stirring occasionally. Beat egg whites until they hold a stiff peak and beat in remaining sugar, a spoonful at a time until smooth and glossy. When lime mixture starts to set, beat until smooth and fold into meringue, with whipped cream. Pour into pie shell and chill.