Step 1

Preheat oven to 350 degrees. Line two baking sheets with Silpat baking mats or parchment paper, and set aside.

Step 2

In the bowl of an electric mixer fitted with the paddle attachment, cream butter and 1 cup sugar on medium speed until light and fluffy, 3 to 5 minutes, scraping down sides of bowl twice. Add egg; mix on high speed until combined. Add lemon zest, and beat to combine.

Step 3

In a large bowl, whisk together flour, baking soda, and salt. Add to butter mixture, and mix on low speed until combined, about 20 seconds. Add candy, and mix to combine. Transfer dough to a sheet of plastic wrap, and freeze until firm, about 30 minutes.

Step 4

Pour remaining 1/2 cup sugar into a large bowl. Shape the dough into 1/2-inch balls. Drop each ball into sugar, and roll, coating completely; use sugar to keep dough from sticking to hands.

Step 5

Working in batches, place sugared balls on prepared baking sheets, 2 inches apart. Gently press balls, flattening to a 1/4-inch thickness. Transfer remaining dough to refrigerator.

Step 6

Bake cookies just until golden, about 10 minutes. Transfer to a wire rack to cool. Repeat with the remaining dough. Store in an airtight container up to 1 week.