In a small saucepan, combine the water and sugar.
Stir over medium heat until the sugar has completely dissolved. (This will create a simple syrup.)
Remove from heat and let cool to room temperature.
In a mixing bowl, combine the cooled simple syrup, freshly squeezed lemon juice, and lemon zest (if using).
Stir well to combine.
Pour the mixture into an ice cream maker and churn according to the manufacturer's instructions. This usually takes about 20-25 minutes, or until the sorbet reaches a smooth and slushy consistency. Transfer the sorbet to an airtight container and freeze for at least 4 hours, or until firm.
When ready to serve, let the sorbet sit at room temperature for a few minutes to soften slightly.
Enjoy!