1. Combine flour and salt in a medium bowl; set aside. Place butter in a large bowl. Using an electric mixer, cream butter for 1 minute; add the sugar and beat for 2–3 minutes, until light and fluffy. Add egg yolk and the Key Lime flavoring and beat for 2 more minutes. With mixer on low speed, slowly add the flour; mixing just until combined. Roll dough into two logs about 2 inches in diameter.

2. In a small bowl, stir together the topping ingredients until the green food coloring is evenly distributed. Transfer topping to a plate or shallow pie pan.

3. Roll each log in sugar/salt topping. Wrap logs in plastic wrap and refrigerate until firm, about 1 hour.

4. Preheat oven to 350°F. Line 2 baking sheets with parchment paper. Remove dough from refrigerator. Slice into 1/4 inch rounds and place on baking sheets. Bake 9–11 minutes or until just browned on the bottom (do not overcook). Allow cookies to cool on baking sheet for 2 minutes before removing. Store in an airtight container for up to 3 days.

Makes about 2 dozen cookies.