Thinly slice a lemon. It is ok to use a lemon without the rind (zest). Take out any seeds.
Boil enough water to cover the lemon slices. Add lemon slices to the water and boil for less than a minute. Drain and rinse with cold water.
Bring 1/2 cup water and 1/2 cup sugar to boil, while stirring. Add the lemon slices, in a single layer. Simmer for 40 minutes.
Place lemon slices on parchment paper. Sprinkle both sides with granulated sugar.
Eat as is or use as a garnish.