1. Preheat oven to 350° F with rack in the lower-third position. Whisk together the sifted almond flour and powdered sugar. Place egg whites in the bowl of an electric mixer. Beat on low until foamy. While beating, sprinkle in the cream of tartar and granulated sugar. Increase speed to medium. Beat for about 4 minutes, or until very voluminous and holding stiff glossy peaks.
2. Remove bowl from the mixer. Add the almond flour mixture all at once. Using a spatula, scrape the spatula all the way around the sides of the bowl and then down through the middle. Repeat this motion 30 to 40 times until batter is smooth and glossy. It should begin to flow off the end of the spatula in a thick, smooth stream.
3. Prepare a pastry bag with a 3/8-inch round tip. Line a baking sheet with parchment paper. Place a small dot of batter on the back-side corners of the paper to hold it in place on the baking sheet. Begin piping one-inch circles. Continue piping, spacing circles an inch apart. Lift the baking sheet a few inches above the countertop. Tap the baking sheet on the countertop twice to release air bubbles.
4. Bake for 15 minutes, or until cookies have risen and they are dry to the touch. Let cool completely on the baking sheet. Remove with a small offset spatula.
5. Prepare a pastry bag with a star tip. Fill with the frosting. Pipe the filling on the flat side of half the cookies. Top the frosting with the other cookie halves, flat-side down. Brush with sparkling sugar or edible glitter.

Per Serving (1): Calories: 140, Fat: 5 g (1 g Saturated Fat), Cholesterol: 20 mg, Sodium: 45 mg, Carbohydrates: 22 g, Fiber: 0 g, Protein: 2 g.