In a small pot, combine the sugar and water and cook over medium heat for 5 minutes, or until the sugar dissolves.
Add the cranberries to the pot and stir. Bring to a boil, then reduce heat to low and simmer for 15 minutes. The cranberries should begin to burst on their own. Using a potato masher or wooden mallet, press down on the cranberries to mash them into a chunky texture.
Remove the cranberries from the stove and add in the orange zest. Stir to combine.
Chill for a minimum of 1 hour so the sauce thickens.