Summarize:

Start by adding 1 cup (240 mL) of water to create a liquid base in the pan. Then mix in 1 ½ cups (345 g) of granulated sugar and the juice from half of a lemon. Do this over a medium-high heat, and continuously stir the mixture to keep the sugar from burning.
Bring the sugar, water, and lemon juice to a boil in a saucepan.