To make the simple syrup, place water and sugar together and set to high heat. Cook and stir until water has dissolved, about 2 minutes.

Remove from heat.

Zest both lemons and add zest to the simple syrup. Allow to cool completely.

While cooling the syrup, puree the raspberries using a food processor and press through a fine mesh sieve. Reserve the puree and discard the seeds.

Once the simple syrup has cooled, combine with puree and add the juice from both lemons.

Place in a dish and freeze, scraping the frozen portions of the granita every 45 minutes or so, until frozen, at least 3 hours. Serve immediately or store covered in the freezer.