¾ c. unsalted butter, room temp
1 c. confectioners’ sugar
Finely grated zest of 2 limes
2 TB fresh lime juice
1 TB pure vanilla extract
1 ¾ c. plus 2 TB all-purpose flour
2 TB cornstarch
¼ tsp. coarse salt
1. Put butter and 1/3 c. confectioners’ sugar in the bowl on electric mixer and mix on medium speed until pale and fluffy. Add the lime zest and juice and the vanilla, and mix until fluffy.
2. Whisk together flour, cornstarch, and salt in a bowl. Add to butter mixture, and mix on low speed until just combined.
3. Divide dough in half. Place each log on an 8 by 12 inch sheet of parchment. Roll in parchment to form a log 1 ¼ inches in diameter, pressing a ruler along edge of parchment at each turn to narrow log. Refrigerated logs until cold and firm, at least 1 hour.
4. Preheat oven to 350. Remove cut logs into ¼ inch thick rounds. Space rounds 1 inch apart on baking sheets lined with parchment paper. Bake cookies until barely golden, about 13 minutes, rotating sheets halfway through. Transfer cookies to wire racks to cool slightly, 8 to 10 minutes. While still warm, toss cookies with remaining 2/3 c. sugar in a resealable plastic bag. Cookies can be stored in airtight containers at room temperature up to 2 weeks.