Photograph: Brett Stevens
Preheat the oven to fan 130°C (see note at the end).
In a large clean bowl, use an electric handwhisk to beat the egg whites to stiff peaks. Gradually add the sugar, whisking well between each addition until glossy and stiff. Draw a 20cm circle on 3 sheets of baking paper. Turn over and use to line 3 baking trays.
Spoon a third of the meringue mixture on to each 20cm circle and spread out to fill each circle.
Turn down the oven to fan 100°C; bake for 1 hour 20 minutes. Turn off the oven, open the door slightly and leave in the oven to cool completely.
Simmer the cranberries with the 3 tablespoons of caster sugar for 5 minutes or until they start to soften. Strain over a bowl; leave to cool.
Whisk the cream with most of the zest, then layer the meringues with the cream and cranberries, adding drizzles of the fruit syrup. Top with the remaining fruit and cream, then sprinkle over the remaining clementine zest. Serve immediately.
Get ahead: if you want to bake all three meringues together, use a fan oven, otherwise bake separately in a conventional oven (or gas equivalent), starting at 150°C and reduce the oven to 120°C for the rest of the time.