Preheat the oven to 350.
Zest and slice your limes, you will probably need 2 depending on size and juiciness.
Work the lime zest into the sugar. You can do this by simply using your fingers to rub the zest into the sugar until well mixed. This helps the lime zest release more flavor.
Add the butter to the lime sugar, and using a fork, begin to work the butter into the sugar. Continue to cream together until smooth and creamy.
Next, add in the egg yolk and mix well.
Lastly, add in the flour and dry ingredients and mix well, until the dough comes together.
*You can either prepare these by the traditional cut out cookie method per these instructions, or you can make them a simple drop cookie using a large cookie scoop (3 tbsp). Now, line a freezer safe cookie sheet with parchment paper and sprinkle tapioca starch on it. Turn out the dough onto the parchment paper. Sprinkle more tapioca starch on top of the dough, then pat into a disk. Place in the freezer for 8-10 minutes. Remove from the freezer and place a piece of parchment paper on top. Roll the dough out into an 8-9in round disk, ensuring the dough stays around ¾-1 inch thick.
Scoop out the cookies, or cut out the cookies in the shape of your choosing, and place them on a parchment paper lined cookie sheet. For soft, bakery style cookies, choose a larger cookie cutter size.
Bake for about 12 minutes for a large cookie, 9-10 minutes for a smaller cookie.
The cookies will spread some, so for that perfect bakery look, here’s my secret: while the cookies are still warm, take a larger cookie cutter than the size of your cookie, place around your cookie and gently push/swirl around your cookie to reshape it before it cools.
While the cookies are baking, mix together the frosting ingredients and whisk until smooth.
Once the cookies are completely cooled, generously drizzle on the frosting, then finish them off with a sprinkle of lime zest.