¾ cup (1 ½ sticks) unsalted butter, at room temperature
1 cup confectioners' sugar (divided use)
2 tablespoons freshly squeezed Key lime juice
2 tablespoons finely grated lime zest
1 tablespoon pure vanilla extract
1 ¾ cups plus 2 tablespoons all-purpose flour
2 tablespoons cornstarch
¼ teaspoon salt
Recipe
Beat the butter and 1/3 cup of the sugar until fluffy with an electric mixer (use a whisk attachment if your mixer has one). Add the lime juice, zest and vanilla; beat until fluffy.
In a medium bowl, whisk the flour, cornstarch and salt. Add to butter mixture and beat on low speed until combined.
Between two 8- by 12-inch pieces of parchment paper, roll dough into two 1 ¼-inch-diameter logs. Chill at least 1 hour.
Heat oven to 350 degrees. Line two baking sheets with parchment. Place remaining sugar in a resealable plastic bag.
Remove parchment from logs; slice into 1/8-inch-thick rounds. Place rounds on baking sheets, spaced 1 inch apart.
Bake until barely golden, about 15 minutes. Transfer to a wire rack to cool slightly, 8 to 10 minutes.
While still warm, place cookies in the sugar-filled bag; toss to coat. Store in an airtight container up to 2 weeks. Bake or freeze remaining dough. Makes about 10 dozen cookies.