Preheat your oven to 350°F (175°C). Grease an 8×8-inch baking pan and set aside.

In a large mixing bowl, whisk together the all-purpose flour, almond flour, granulated sugar, powdered sugar, salt, and lemon zest.

Cut in the cold vegan butter using a pastry cutter or two knives until the mixture forms pea-sized crumbs. Gradually drizzle in the melted coconut oil, mixing gently until the dough just holds together.

Press the crust mixture evenly into the bottom of the prepared baking pan. Bake for 25-30 minutes, or until the edges are lightly golden brown.

While the crust bakes, combine the granulated sugar, cornstarch, and salt in a medium saucepan. Whisk in the lemon zest, lemon juice, and water until smooth. Add the vegan butter and cook over medium heat, whisking constantly, until the mixture thickens and turns glossy (about 5-7 minutes).

Remove from heat and stir in the vanilla extract and turmeric (if using). Strain the mixture through a fine-mesh sieve for a smoother filling, if desired.

Allow the crust and filling to cool completely. Pour the filling over the baked crust, spreading it evenly. Cover and refrigerate overnight or until set.

Dust the top with powdered sugar, slice into bars, and enjoy!