Whisk together powdered sugar and almond flour. Sift mixture through a fine sieve into a large bowl, discard anything too coarse to go through.
Using either a hand or stand mixer, beat the egg whites, salt and cream of tartar on medium speed until frothy. Increase speed to medium high and gradually add the superfine sugar (sugar that I ran through my blender) until your peaks are stiff and shiny (about 5-8 minutes).
Transfer beaten egg whites to large bowl and fold into almond flour mixture until completely incorporated but not so much that it resembles pancake batter.
Place batter in a pastry bag with a wide tip pipe out bunny shape, beginning with head and then adding the ears. Once cookie sheet is full, tape the entire sheet twice on the counter to remove air bubbles.
Allow to sit at room temperature until the surface of the cookies aren't sticky anymore. Depending on your humidity, this may take anywhere from 15-60 minutes.
Bake cookies until they rise enough to create "foot," approximately 16-20 minutes. Remove from heat and immediately transfer to cooling rack.