In a medium bowl, whisk together the gluten free 1-to-1 baking flour, cocoa powder, baking powder, and salt. Set aside.
In a large bowl, whisk together the granulated sugar, vegetable oil, eggs, and vanilla extract until smooth. Stir in the melted and cooled chocolate until well combined.
Add the flour mixture to the wet ingredients and stir with a rubber spatula until a thick, sticky dough forms. Cover the bowl with plastic wrap and refrigerate for at least 2 hours or until the dough is firm enough to roll.
Preheat the oven to 350 F and line two baking sheets with parchment paper. Place the powdered sugar in a shallow bowl. Scoop about 1 tablespoon of dough at a time, roll into a ball, then roll generously in the powdered sugar until completely coated. Place the cookies about 2 inches apart on the prepared baking sheets.
Bake for 11 to 13 minutes until the edges are set and the tops are crackled but still slightly soft in the center. Let cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.