Once the syrup is drained away, candied lemon zest can be stored in an airtight container, its bottom lined with sugar, up to 1 week.
Using a vegetable peeler, peel zest from lemons in strips, using the entire length of the lemon. Use a knife to remove any white pith from back of zest.
Bring 4 cups water to a boil in a medium saucepan. Add zest; blanch for 1 minute, drain, and rinse under cold water.
In medium saucepan, combine sugar and 2 cups water; bring to a simmer. Cook until sugar dissolves completely, about 2 minutes. Add lemon zest. Simmer until translucent, about 30 minutes. Remove from heat, and let zest cool in syrup.
At this stage, zest and syrup can be transferred to an airtight plastic container and stored in the refrigerator for up to 1 month. To serve, drain zest, and place on wire rack so excess syrup can drip away, then roll in sugar.