- With the rack in the lowest position, preheat the oven to 180 °C (350 °F).
- In a saucepan, bring the lemon juice and butter to a boil. Remove from the heat.
- In another saucepan, with a whisk, combine the eggs, sugar, and salt until smooth. Gradually stir in the hot juice and butter mixture. Cook over medium heat, stirring with a whisk until the mixture thickens, about 10 minutes. Remove from the heat once it first boils.
- Strain the filling through a sieve. Pour into the crust and bake for about 12 minutes. Let cool then refrigerate until completely chilled, about 2 hours.
- In the upper part of a double boiler, heat the sugar and egg whites, stirring constantly, until the sugar has dissolved and a candy thermometer reads 60 °C (140 °F). Remove the bowl from the water bath and beat the mixture until stiff peaks form.
- With the rack in the highest position, preheat the oven’s broiler.
- Spread the meringue over the cooled pie, covering completely up to the edge of the crust.
- Carefully brown under the broiler. Consume preferably the same day.
You can also spoon the meringue into a pastry bag fitted with a star tip to form rosettes on the pie.