Wash the lemon and cut it in half. Squeeze out lemon juice for later use.
Add sugar and water into a stainless steel pot and stir well.
Boil over medium heat and pour in lemon juice. Remember not to stir afterwards.
Turn the heat down and cook slowly. During the cooking process, there will be crystals on the wall of the pot. Just brush it with water.
Be sure to cook with low fire until the color is slightly darker and thicker, about 1 hour, and put it in a sealed can after cooling.