Whisk the gluten free flour, cocoa powder, baking powder, and salt in a medium bowl.

In a large bowl, whisk the 3/4 cup granulated sugar, oil, eggs, and vanilla until smooth and slightly thick.

Fold the dry mixture into the wet mixture just until a dark, sticky dough forms. Refrigerate, covered, for at least 2 hours.

Preheat the oven to 350°F (175°C). Shape chilled dough into 1-tablespoon balls, roll first in extra granulated sugar, then coat heavily in powdered sugar.

Place on parchment-lined sheets and bake 10 to 12 minutes. Cool on the sheet 5 minutes, then transfer to a wire rack.