Bake a bottom pie crust according to recipe directions.
Make the cranberry pie filling
Combine orange juice, sugar, and cranberries in a saucepan and bring to a slow boil.
Allow the cranberries to a boil until they pop open.
Pour the cranberry sauce through a mesh strainer and press to get all of the liquid out of them.
Put the cranberry liquid back into the saucepan along with 3 tablespoons of cornstarch mixed with 3 tablespoons of cold water.
Stir constantly until it starts to boil and thicken, then turn off the heat and let it cool for a few minutes.
Pour the hot cooked cranberry filling into your prebaked pie crust and place it in the fridge to cool for at least an hour before topping with vegan meringue.
Make the meringue
Add aquafaba (chickpea liquid) to the bottom of a large mixing bowl with the cream of tartar or lemon juice and beat for 7 minutes until it forms a stiff meringue.
Add 2 tsp of vanilla and beat again for another minute.
Turn off the beaters and make your syrup.
Make the syrup to set the meringue
In a small saucepan, add water and agar agar and boil for 3 minutes.
Then add the sugar and boil for 3 more minutes stirring constantly.
Then immediately pour the hot syrup slowly into your meringue mixture with the beaters set to medium.
Beat the syrup and the mixture for about 30 seconds until it is well incorporated, and your meringue looks shiny.
Quickly top your pie with the meringue spreading it evenly over the top and making peaks by lifting up the spatula. (You must work quickly because the meringue will start to set once it cools).
Let your pie cool in the fridge for another hour allowing it to set completely.
Then use a kitchen torch to toast the top of the meringue giving the peeks some golden-brown color. (This is optional and only for aesthetics).
Place the pie in the fridge for at least 3 more hours to set before cutting.
Notes
Allow the cranberry pie filling to cool in the fridge for at least 1 hour before adding the meringue topping.
Measure your agar agar carefully, slight changes in the amount of powder will affect the firmness of your pie.
Once you mix the syrup into the meringue, work quickly to put it on top of your pie. You will only have about 1-2 minutes before it starts to firm up and set.