Add the water and sugar to a sauce pan. Bring this to a boil while continuously stirring.
Slice the lemon into ¼" circular slices and add those lemon slices to your sugar water mixture. Reduce your heat to medium low. Let this simmer for 20-25 minutes.
Remove the pan from the heat, remove the lemons from the pan, and let the lemons cool and harden. They usually cool pretty quickly so they should harden up soon after taking off the heat.
Serve with your favorite dessert or drink and enjoy!