Place the water, cranberries and sugar into a small saucepan
, set over medium-high heat and simmer
until the berries begin to pop, approximately 7 minutes. Remove from the heat. Puree with a stick blender, blender
or food processor
, for 1 minute. Pass the mixture through a fine mesh strainer directly into a metal 13 by 9-inch pan. Do not press on the skins. Simply allow the juice to drip through the strainer
. Add the zest
and stir to combine. Place in the freezer until set, at least 6 hours and up to overnight. Once frozen, scrape the mixture with a fork to create a shaved ice texture. Serve immediately.