In an ungreased skillet, on medium heat cook the pepita seeds while occasionally stirring for 5 minutes until slightly darker and fragrant. (If your pepitas are salted and roasted, skip this step.) Place the pepitas in a blender or food processor and pulse until ground to the texture of rough cornmeal (be careful when doing this, if you grind them for too long it will turn into pepita butter).
Cream together the butter and the sugar in a mixing bowl. Add the lime juice, 1 teaspoon of lime zest, vanilla, flour, sea salt and the ground pepitas. Mix until well combined. Cover and chill in the refrigerator for 1 hour.
Once the dough has cooled, preheat the oven to 350 degrees and line a baking sheet with parchment paper.
Remove the dough from the refrigerator. To form the cookies, take 1 tablespoon’s worth of dough, form it into a ball and then roll it into a 3-inch-long log. Bend it in the center to form a crescent. The cookies don’t spread much, so you only need 1/2 an inch or so between them on the sheet. Bake the crescents for 15-18 minutes or until lightly browned. They will still be soft when they come out of the oven but will harden as they cool.
While the cookies are baking, combine the powdered sugar with the remaining 1/2 teaspoon of lime zest. You can do this in a food processor if you want the lime zest extra fine or just stir the zest into the sugar. Once the cookies are done, cool on a rack for 10 minutes and then roll the crescents in the powdered sugar.
Cookies will keep in an airtight container for a week. They can be delicate, so handle with a bit of care.