Preheat the oven to 350 degrees.
Separate the eggs, reserving the whites and yolks in separate bowls. Set the egg whites aside.
Beat the egg yolks until frothy.
Add the sweetened condensed milk.
Leaving the mixer on, add the lemon juice.
Once combined, pour the mixture into the pie crust.
In a separate bowl, beat the reserved egg whites at medium-high speed until soft peaks form.
Reduce the speed and slowly add the sugar and the cream of tartar. Increase the speed back to medium-high and continue to beat until stiff peaks form.
Top the pie with the meringue.
Bake for about 10 minutes or until the meringue is browned a little on top.
Cool completely, then chill the pie in the refrigerator for at least four hours.