Bring the water and sugar to a gentle boil. Once the sugar has dissolved, remove from heat and stir in the lemon juice.

Strain the mixture through a fine mesh sieve and let it cool. Once cooled, pour it into a plastic or metal bowl and place it in the freezer.

After 30 minutes, take out the granita and stir it with a whisk to break up the ice crystals. Repeat this process every 30 minutes for 5 to 6 times, until the granita turns white and fluffy.