Simple Syrup - combine ¼ cup sugar and ¼ cup water in a small saucepan. Bring mixture to a boil and stir until all the sugar is dissolved. Cool. You will have extra simple syrup - place in a container and refrigerate. Use to sweeten ice tealemonade or in a cocktail!
Stem the grapes and place them in a blender or food processor. Puree grapes. Drain the grape mixture through a mesh strainer, pressing down on the solids to release as much juice as possible. This should yield about 3 cups of juice!
I a bowl or 4 cup measuring cup add the juice, ½ cup Dubonnet Rouge and 2 Tablespoons cooled simple syrup. Stir to combine. Taste and add more simple syrup if needed. The mixture should be sweet, but not overpoweringly so. I used ¼ cup, but remember how much you need will depend upon how sweet your grapes are! Pour mixture into a 8 x 8 metal or glass baking pan. Freeze for 1 hour.
Remove pan and, using a fork, scrape the surface and edges to release and flake the frozen mixture. Return the pan to the freezer and freeze for another hour. Remove and scrape again - your goal is to create shard/chucks about ¼ of an inch. Return the pan to the freezer and freeze for another hour. Remove the pan and scrape again with a fork. By now, the majority of the mixture should be frozen and should have a slushie like texture. If liquid still remains, return the pan to the freezer and scrape again after freezing for another hour.
NOTE: the addition of the alcohol will allow the mixture to remain somewhat soft so it will not achieve a hard freeze - which is a good thing! After all the liquid is frozen, scrape again to "fluff up" the granita. Using a large spoon gently spoon ½ cup of the granita into each serving bowl or glass. Makes 8 ½ cup servings.