Preheat the oven to 350°F and line 2 baking sheets with parchment paper.
In a small bowl, mix together the gluten free flour, baking powder, xanthan gum, and salt. Set aside for a moment.
In a medium-sized bowl, beat the egg whites until foamy using an electric mixer (stand mixer or hand mixer with both beaters).
After the egg whites are foamy, add in 2 tablespoons (26g) of the sugar and the vanilla extract. Continue to beat the egg whites until stiff peaks form (about 2 minutes of mixing).
In another medium-sized bowl, beat the yolks and the remaining sugar together using the electric mixer. The egg and sugar mixture should become thick and pale yellow (about 2 minutes of mixing).
Sift the flour mixture into the egg yolk mixture and gently fold in. The mixture may look thick and lumpy.
Fold the egg yolk + flour mixture into the bowl containing the egg whites. Handle the mixture gently and as minimally as possible to not ruin the aeration. The dough may look lumpy (and that’s ok).
Using a pastry bag, or a large sandwich bag with the corner cut off, and a ½”-1” (1-2 ½ cm) tip: pipe cookies that are 1” wide by 3” long (2 ½ x 7 ½ cm) on the parchment paper. Spread the cookies about 1” (2 ½ cm) apart so they don’t touch during baking.
Bake one sheet of cookies at a time. Immediately before baking, dust the cookies with a generous amount of icing sugar. They should be completely covered in icing sugar (as will the parchment paper).
Bake cookies for 10-13 minutes until they are slightly firm but still spongy.
Cover remaining cookies on second cookie sheet with icing sugar and bake as directed.
Cool cookies on a wire cooling rack.
