Heat oven to 400℉.
Line a jelly roll pan (9½ inches x 14½ inches) with parchment paper and spray with baking spray. Set aside.
In a small bowl, sift flour and cocoa powder. Set aside.
With an electric mixer fitted with the whisk attachment, beat egg whites until foamy.
Slowly stream in the 3 Tablespoons sugar.
Beat to medium soft peaks. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, beat egg yolks, eggs, and ½ cup sugar to ribbon stage, about 7 minutes.
Fold meringue into egg mixture in 3 stages.
Fold in dry ingredients.
Spread evenly in prepared pan, making sure to fill in corners.
Tap on counter to remove air bubbles.
Bake at 400℉ for 7-9 minutes, or until just done.
While the cake is baking, place a piece of parchment paper bigger than the cake out on your work surface.
As soon as you remove the cake from the oven, dust it heavily with cocoa powder.
Immediately turn cake out onto the parchment.
Remove jellyroll pan.
Peel the parchment off the cake.
Beginning with a short end, roll up jelly roll style along with the parchment you turned it out on.
Set aside to cool for 15-20 minutes. It should still be a little bit warm.
Unroll cake and allow it to cool completely