Add 1/2 cup aquafaba (bean liquid) to the bottom of a large mixing bowl with 1/4 tsp cream of tartar or lemon juice. Beat for 7 minutes until it forms a stiff meringue.
Add 2 tsp of vanilla and beat again for another minute before turning off the beater and making your agar agar syrup.
Make the syrup to stabilize the meringue
In a small saucepan, add 1/2 cup water and 3/4 tsp agar agar and boil for 3 minutes.
Then add 3/4 cup sugar to the agar mixture and boil for 3 more minutes stirring constantly.
Immediately pour the hot syrup slowly into your meringue mixture with the beaters set to medium.
Beat the syrup into the aquafaba 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.
Use a kitchen torch to toast the top of the meringue giving the peeks some golden-brown color. (optional)
Notes
Measure your agar agar carefully, slight changes in the amount of powder will affect the firmness of your pie.
Work quickly when making the aquafaba meringue. It will set once it cools, so it needs to be added to the pie quickly while it is still warm.
I don't recommend toating the top of your pie in the oven. The meringue can become too hot and deflate or melt. A kitchen torch works best.