Place cashews, coconut cream, lemon zest, lemon juice, maple syrup, vanilla, cornstarch, cream of tartar, and salt into a high powered blender (like a Vitamix) and blend until very smooth and creamy — there should be no lumps.
Pour into the slightly cooled crust then bake in the preheated oven for 25 minutes — it will still be quite jiggly in the center.
Cool at room temperature for 30 minutes.
Place in the fridge to set, at least 2 1/2 hours, but preferably overnight.
Right before serving, dust with powdered sugar, slice into squares, and enjoy!