Use these lemon slices as a dessert or cocktail garnish.
Using a mandoline or chef's knife, slice the lemons into rounds, as thin as possible.
In a medium saucepan, combine sugar and 1 cup water; bring to a boil over medium-high heat. Cook until sugar has dissolved and mixture is simmering, about 10 minutes. Remove pan from heat, and place lemon slices in hot syrup; cover. Let slices rest in pan until cooled to room temperature, about 1 1/2 hours. Transfer slices and syrup to an airtight container; refrigerate for at least 3 days. Slices will keep, refrigerated, up to 1 month.