How to Make It
In a small saucepan, combine the water and sugar and bring to a simmer, stirring to dissolve the sugar. Remove from the heat and let cool to room temperature.
In a 9-by-13-inch glass or ceramic baking dish, stir the sugar syrup into the blood orange juice. Freeze for about 1 hour, or until ice crystals form around the edge. Using a fork, stir the crystals into the center and freeze for about 30 minutes, until a thicker rim of crystals forms around the edges. Stir again and freeze for about 1 hour longer, stirring every 15 minutes or so until all the juice is frozen.
Scoop the granita into 8 bowls, top with vanilla ice cream and serve immediately.