Line a baking sheet with parchment paper or silicone mat, lightly dust with sugar if desired.

Combine water, lemon juice, and corn syrup in a heavy-bottomed saucepan over medium heat, stirring until sugar dissolves.

Slowly whisk in granulated sugar until fully dissolved.

Attach a candy thermometer and bring mixture to 300°F (hard-crack stage). Avoid stirring once boiling.

Remove from heat and stir in lemon zest and optional food coloring.

Pour hot syrup onto prepared sheet, spreading thinly or leaving as drops.

Shape candies with a buttered knife or scissors while slightly warm.

Cool completely at room temperature.

Optionally roll candies in sugar to prevent sticking and store in an airtight container.