Place the almonds and powdered sugar in a food processor and run for several minutes, occasionally stopping to scrape the sides. Sift the mixture into a large bowl and discard any pieces that don't pass through the sieve.

In a large metal bowl, add the egg whites and cream of tartar. Begin whipping on medium-high with a whisk attachment until the eggs become foamy and white. Scrape the bowl, then add a tablespoon of granulated sugar and whip again for about 20 seconds. Scrape the bowl and repeat until all the granulated sugar has been added. Scrape the sides one last time then allow to whip at medium-high just until stiff peaks form.

Add the lime zest and a few toothpick draws of yellow and green gel food coloring, then sift about ⅓ of the almond meal/powdered sugar mixture into the bowl. Slowly and carefully fold the egg whites, by scraping the sides to the bottom of the bowl and then back over the top until the sugar flour is incorporated. Repeat until the all the sugar flour is mixed in, being careful to not beat the egg mixture.

Carefully spoon into a pastry bag prepped with a 1 inch round tip and pipe 1 ½ inch circles onto baking sheets covered with parchment paper. Tap the baking sheets again a flat surface to release any trapped air bubbles.

Allow the macarons to rest for 20-60 minutes, or until they lose their shine and are no longer tacky to the touch.

Bake in a 300 degree oven for 13 minutes, or until the bottoms are just barely starting to brown.