Cook over medium heat, stirring constantly until mixture thickens and boils. Boil for one minute
Add a little of the hot mixture into your 3 egg yolks. Then pour the hot mixture into the pan with the rest of the hot mixture and stir. This prevents the hot mixture from cooking the egg.
Boil one minute longer, stirring constantly. Remove from heat and continue to stir until smooth.
Add in butter, lemon juice and lemon rind and pour into baked pie shell
Cover with meringue. Making sure it covers the whole service of the pie.
Bake until a light golden brown at 400 degrees for about 10-12 minutes.
Cool and serve.
Meringue
Beat egg whites and cream of tartar until foamy.
Add in sugar one tablespoon at a time until stiff and glossy
Pile meringue onto pie filling
Be sure and seal the meringue onto the edge of crust to prevent shrinking.
if the filling is exposed to heat it will "weep"
Swirl the meringue with the bottom of a spoon for a decorative top.
Bake until lightly golden brown. Cool gradually, away from drafts
Notes
Allow pie to cool completely on a wire rack at room temperature before serving. If the pie is warm, the lemon filing will be runny when you cut into it. You can chill it for 2-3 hours before serving also if desired.
Cut the cooled pie with a wet knife to prevent the meringue from sticking to it.
Yes, keep leftover pie in the refrigerator, loosely covered with plastic wrap. Don't let the pie sit out at room temperature for more than a couple of hours. It will last for 2-3 days in the refrigerator but will begin to "weep" the longer it is in the fridge.