In a medium bowl, whisk together the gluten-free flour, cocoa powder, baking soda and salt. Set aside.
In the bowl of a stand mixer, or using a hand mixer, beat the butter, granulated sugar and brown sugar together until smooth.
Add the eggs and vanilla and beat on medium until light and fluffy, about 2-3 minutes.
Add the dry ingredients to the wet ingredients and mix until combined. Scraping down the bottom and sides of the bowl halfway through.
Cover the bowl and refrigerate the dough for at least 2 hours, or up to 3 days.
Preheat the oven to 350°F. Line large baking sheets with parchment paper or silicone baking mats.
Scoop the cookie dough into round balls, about 2 tablespoons per ball. Roll each dough ball in the granulated sugar, then roll generously in the powdered sugar.
Place on the prepared baking sheet, about 2 inches apart.
Bake for 10-12 minutes, or until the edges are set, but the centers are still soft.
Remove from the oven and cool on the baking sheet for 5 minutes. Transfer to a wire rack to cool completely.