Begin by preparing your baking sheets: line them with parchment paper or silicone mats, and if desired, use a template to ensure consistent sizes.

In a food processor, combine the almond flour and powdered sugar. Pulse until finely ground. Sift the mixture into a bowl to remove any larger pieces, ensuring a smooth macaron shell.

In a clean mixing bowl, beat the egg whites on medium speed until they become frothy. Add the cream of tartar and continue to mix until soft peaks form.

Gradually add the granulated sugar while continuing to whip the egg whites. Increase the speed to high and beat until stiff peaks form and the meringue is glossy. This may take about 5-7 minutes.

Gently fold in the sifted almond flour and powdered sugar mixture with a spatula. Use a technique called macaronnage: fold until the batter flows like lava and leaves a ribbon when lifted. Be careful not to overmix.

If using food coloring, add it at this stage and gently mix until the desired color is achieved.

Transfer the batter to a piping bag fitted with a round tip. Pipe uniform circles onto the prepared baking sheets, leaving space between each macaron.

Tap the baking sheets on the counter to remove any air bubbles. Let the piped macarons rest at room temperature for 30-60 minutes, until a skin forms on the surface.

Preheat your oven to 150°C (300°F). Bake the macarons for 15-20 minutes, or until they have risen and formed a 'foot.' They should not be browned.

Allow the macarons to cool completely on the baking sheets before carefully removing them.

Once cooled, pair similar-sized shells and fill them with your chosen filling. Sandwich them together and let them age in the refrigerator for at least 24 hours for the best flavor.