Line two large baking pans with parchment paper or Silpat mats.
Heat a small saucepan of simmering water over medium-low heat. Add the egg whites and granulated sugar to a heatproof bowl and set it over the simmering water. Whisk constantly until the sugar has fully dissolved, about 2 minutes.
3 large egg whites, ½ cup granulated sugar
Transfer the egg mixture to the bowl of a stand mixer fitted with the whisk attachment and beat on medium-high speed (Kitchenaid #8) until stiff peaks form, about 5 minutes.
Using a fine-mesh sieve, sift the powdered sugar and almond flour into the egg white mixture, making sure to discard any large lumps.
⅘ cup powdered sugar, 1 cup almond flour
Gently fold the dry ingredients into the egg whites, making sure not to deflate the egg whites at this point.
Once all of the dry ingredients have been incorporated, add the gel food coloring, if using. (see notes)
Gel food coloring
Continue to fold the meringue, but this time gently smush the batter against the sides of the bowl before folding it back together.
Continue to smush and fold the meringue a few times before testing to see if it has reached the Figure 8 stage. The meringue is ready to pipe when you can draw a figure 8 without the stream breaking.
Transfer the meringue to a piping bag fitted with a small round tip (I like a Wilton #10). Pipe 1-inch macaron shells onto the tray, making sure to pipe them at least 2 inches apart. Once you’ve finished piping the first tray, hold it a few inches off the counter and drop it straight down. Drop the tray another 5-6 times, or until it looks like any large air bubbles have popped. Repeat with the second tray.
Set the trays aside to rest for at least 25 minutes. They’re ready to bake when you can touch them gently without the meringue sticking to your finger.
While the macarons rest, preheat your oven to 325°F. Use an oven thermometer to make sure your oven reaches 325°F. Most ovens run hot, so you may have to set the temperature a little lower to actually reach 325°F.
Bake the macarons, one tray at a time, for 13 minutes. If your oven has hot spots, make sure to turn the tray halfway through baking so the feet rise evenly.
Allow the macarons to cool to room temperature before trying to remove them from the pan. This will help prevent sticking.