This easy-to-make dessert takes several hours to chill, but your family will agree that it's worth the wait. With its fluffy custard topping, the pudding tastes almost like a crustless lemon meringue pie.
In a large bowl, sprinkle the gelatin over 1/4 cup of cold water and let it stand for 1 minute. Add 1 cup of boiling water, 1/2 cup of sugar, and the lemon juice. Stir until all of the sugar has dissolved and place the mixture in the refrigerator to thicken for about 2 hours.
Once the gelatin has chilled, prepare the powdered egg whites according to the package directions and beat with an electric mixer until stiff peaks form, about 5 minutes. In a separate bowl, beat the gelatin with an electric mixer until it's a frothy foam, about 4 minutes.
Add the egg whites to the gelatin and beat until well blended, about 1 minute. Refrigerate this mixture for a minimum of 2 hours.
While the gelatin mixture chills, begin preparing the custard sauce by beating the egg yolks and setting them aside.
Scald the milk by heating it on medium high until small bubbles appear, about 4 minutes.
Pour the milk, egg yolks, and 1/4 cup of sugar into the top of a double boiler sitting over simmering water. Stir the mixture constantly to prevent lumping until the custard has thickened and lightly coats a metal spoon, about 10 to 13 minutes; a finger drawn across a coated spoon should leave a clear path. Don't cook the custard too long or it will curdle.
Remove the custard from the heat and stir in the vanilla extract. Let it cool to room temperature, stirring often. Cover and refrigerate for a minimum of 1 1/2 hours. Serve the gelatin mixture topped with the custard. Makes 6 servings.