To make cinnamon sugar roasted grapes, preheat the oven to 200°C fan forced. Line a roasting pan with baking paper (try to extend the paper up the sides of pan to collect syrup). Leaving the grapes attached to the stems, snip half the grapes into 8 small bunches. Remove the remaining grapes from stems. Place the grape bunches and loose grapes in the pan. Sprinkle with cinnamon sugar. Turn to coat. Spoon over the rosewater. Roast for 25 minutes, turning the bunches and stirring the grapes after 15 minutes. Allow to cool completely. This can be done the day before and store covered in the fridge.
Reduce the oven to 100°C fan forced. Grease and line two oven trays with baking paper.
Beat the egg whites in a large bowl of an electric mixer to soft peaks. Add the sugar, 1 tablespoon at a time, beating between each addition until dissolved. Beat for a further 5 minutes, or until thick and glossy. Fold in the cornflour and vinegar. Use a large spoon to dollop 4 oval shaped clouds onto each tray, allow plenty of space for spreading.
Bake the pavlova clouds for 1 hour 20 minutes, or until dry and crisp. Turn the oven off. Cool the pavlova in oven with door ajar for 3-4 hours.
TipYou can buy rosewater at gourmet greengrocers or mix ½ cup (125ml) water with 3 teaspoons rosewater essence to make your own.