For the crust: In a bowl, mix flour and powdered sugar. Cut in vegan butter until crumbly. Add cold water, 1 tablespoon at a time, until dough forms. Press into a tart pan. Bake for 15 minutes.
For the filling: In a saucepan, whisk lemon juice, coconut milk, sugar, cornstarch, and turmeric. Cook over medium heat until thickened. Pour into baked crust.
For the meringue: Whip aquafaba and cream of tartar until soft peaks form. Gradually add powdered sugar and whip until stiff peaks form. Spread over lemon filling.
Bake for another 15 minutes until meringue is golden.