- On a work surface, using a vegetable peeler, remove the zest from half of the lemon. Using a knife, finely chop the zest.
- In a small pot, bring 1 cup (250 ml) of the water, the sugar and chopped lemon zest to a boil just until the sugar has dissolved. Pour into a large bowl. Add the remaining water and the lemon juice. Cover and refrigerate for 4 hours.
- Pour the chilled mixture into an ice cream maker. Churn for 20 minutes (or according to the manufacturer’s instructions), until it resembles the texture of granita.
- Serve in glasses with wide straws. The slushie mixture can be kept chilled in the ice cream maker for up to 1 hour.