Combine all ingredients and stir until sugar melts.
Pour mixture into 9 by 13−inch metal pan and place on level shelf in freezer for half an hour. (Mixture should only come about 1/4−inch up the side of the pan.)
Remove and use a dinner fork to scrape any ice crystals that have formed on the side or bottom of the pan.
Return to freezer and repeat scraping every 20 to 30 minutes for 3 to 4 hours.
Once mixture is thoroughly frozen, fluff with a fork and allow flakes to \"dry\" in freezer another half hour before serving.
When served, the granita should look like a fluffy pile of dry brown crystals.
Scoop into goblets and top with barely sweetened whipped cream, add additional citrus zest if desired.