Preheat the oven to 180°C fan and grease a round pie dish.
Add the digestive biscuits into a food processor and blitz until they have the texture of fine sand. Transfer the ground biscuits into a bowl.
Melt the vegan butter and add it into the bowl with the ground biscuits. Mix.
Now, add the rice malt syrup and mix until combined.
Transfer the base into the greased pie dish and press it down evenly.
Bake the base for 15 minutes at 180°C fan. Cool completely before adding the filling.
Filling
Add the sweetened coconut condensed milk, lime juice, silken tofu, corn starch and salt into the food processor and blend until smooth. (The mixture will be quite watery at this point but that's nothing to worry about.)
Transfer the mixture into a saucepan and cook it on low-medium heat for about 7 minutes until the filling starts to thicken. Stir regularly, the mixture should not be boiling.
Pour the filling into the cold base.
Bake the pie for 15 minutes at 160°C fan. Once baked, the pie will still be a bit wobbly. Let the pie cool down on the countertop for about 20 minutes before adding clingfilm onto the top. Lay it against the filling to prevent it from drying out.Now, place the pie into the fridge and let it rest until completely cold. You can also leave it there overnight and continue with the topping the next day.
Topping
Add the aquafaba and cream of tartar into a bowl and whip for about 15 minutes until the aquafaba is white and fluffy and forming soft peaks. A stand mixer works best for this, but an electric mixer is ok too.
Slowly pour in the sugar while continuing to whip. Whip until the meringue creates semi-stiff peaks.
Remove the clingfilm from the pie and add the meringue on top of the filling.
To finish off, grate some lime zest on top of the meringue. Serve the pie cold.The pie stores well for up to 3 days in the fridge.