Mix almond flour and powdered sugar in food processor (40-50 seconds).
Add cacao powder to almond mixture and pass through a fine sieve.
Add a pinch of salt to egg whites and beat until foamy.
Slowly add sugar and beat until firm peaks form.
Fold the dry mixture into the meringue, keep folding the batter until it reaches a honey-like consistency.
Transfer the batter to the pastry bag.
Line two baking sheets with parchment paper. To make all macarons look the same size, print out a 2.5 cm macaron template, place under parchment paper and trace the outlines. You can also use a silicone mat.
Holding the bag vertically and close to the baking sheet, pipe circles. Tap the baking sheet a few times on the counter to release any air bubbles, and to make them look round. Let them sit at room temperature for 30-45 minutes, until skin forms on the shells.
Preheat the oven to 320 degrees F. Bake for 15 minutes (one sheet at a time). Each oven temperature is different so keep an eye on them. Allow the cookies to cool completely on the baking sheet before removing them. Pair the cookies up according to size.