In a large bowl, beat the eggs and granulated sugar together using an electric mixer until pale and thick. This may take about 5-7 minutes.
Add the vanilla extract and beat for an additional minute.
In a separate bowl, sift together the gluten-free flour, cocoa powder, baking powder, and salt.
Gently fold the dry ingredients into the egg mixture in batches, being careful not to deflate the batter.
Pour the batter into the prepared jelly roll pan, spreading it out evenly.
Bake in the preheated oven for 12-15 minutes or until the cake is springy to the touch.
While the cake is baking, place a clean kitchen towel on the counter and sprinkle it generously with powdered sugar.
When the cake is done, immediately invert it onto the prepared towel. Carefully peel off the parchment paper.