Preheat oven to 350°F.
Beat condensed milk, lemon juice, and egg yolks together in a bowl. Pour mixture into graham cracker pie shell. Bake for 15 minutes. Allow to cool.
Turn oven to broiler (500°F). Move oven rack to top position.
In a separate mixing bowl, beat egg whites to foamy. With mixer running, slowly pour sugar into whites. Beat on high until meringue is stiff and forms spikes. (This is referred to as 'stiff peaks'.)
Spread meringue evenly on top of cooled pie, covering the crust completely.
Brown meringue on top rack in oven until golden-colored.
Allow pie to chill 2 hours.