Candied Lemon Slices for Lemon-Thyme Tower Cake

Using a Japanese mandoline, slice the lemon as thinly as possible; set slices aside.

In a medium saucepan, combine sugar and 2 cups water. Bring liquid to a boil over medium-high heat Add lemon slices; return to a boil. Remove pan from heat. Let cool completely; transfer syrup and slices to an airtight container. Store, refrigerated, up to 1 week.