Preheat your oven to 300°F (150°C) and line a baking sheet with parchment paper.
In a food processor, pulse the powdered sugar and almond flour together until well combined. Sift the mixture into a bowl to ensure there are no lumps.
In a separate bowl, beat the egg whites until foamy. Gradually add the granulated sugar while continuing to beat until stiff peaks form.
Gently fold the almond flour mixture into the egg whites in three batches, being careful not to deflate the mixture. If desired, add a few drops of food coloring.
Transfer the batter to a piping bag fitted with a round tip. Pipe small circles onto the prepared baking sheet, leaving space between each one.
Tap the baking sheet on the counter a few times to remove any air bubbles, then let the macarons sit at room temperature for about 30 minutes to form a skin.
Bake the macarons in the preheated oven for 15-20 minutes, or until they are set but not browned. Let them cool completely on the baking sheet.
Once cooled, pair up the macaron shells by size and fill them with your desired filling. Sandwich them together gently.
Store the filled macarons in an airtight container in the refrigerator for at least 24 hours before serving to allow the flavors to meld.
