Combine the 10 packets of acesulfame-K, flour, and salt in a saucepan.
Add the milk and stir to combine.
Bring to a boil and cook for 1-2 minutes, stirring with a wire whisk.
Turn off the heat.
In a separate container, add a small amount of the hot milk and the egg substitute.
Return this to the saucepan and cook for several minutes over low heat, stirring with a wire whisk.
Let cool for a few minutes.
Add the sour cream, vanilla extract, lemon peel, lemonjuice, and prune pieces.
Whisk together.
Pour into a prepared pie shell or into an empty 9 inch (23 cm) pan if you wish to reduce calories.
Then prepare the topping.
Beat the egg whites with an electric mixer, add in the cream of tartar near the end.
Then beat in the sugar, acesulfame-K, and cardamom.
Spread the meringue over the top of the pie.
Use a rubber spatula to be sure the topping goes all the way to the edges.
Bake in a preheated 350°F (180°C) oven for 13 minutes.
Cool in the refrigerator.