Preheat the oven to 350 degrees F (177 C). Grease an 8x8 inch square baking dish with butter/oil or line with parchment paper. Mix the powdered sugar, coconut, coconut flour, GF flour, and salt together. In a microwave safe bowl, melt the butter/coconut oil. Add the vanilla and the dry ingredient mixture, and mix until a slightly crumbly dough forms. Press the dough into the prepared baking pan to create a flat even layer. Bake for 12-15 minutes until golden brown.