Remove the seeds from the water-melon flesh, purée it in a blender until smooth and pour into a saucepan. Add the sweet sparkling wine and yoghurt and cook over a low heat, half-covered, stirring now and then until the mixture is reduced to the third part. Add the cinnamon and stir.
Meanwhile soak the leaf gelatine in cold water, squeeze and melt in the warm mixture. Let the mixture cool and then pour it into a pudding mould. Chill overnight.
Before serving, turn out your cake on the serving platter. If this operation is difficult, you can plunge the mould into hot water for few seconds. Arrange around a fruit salad made with melon, kiwi fruits, lemon juice and ice sugar.

Note

• - It's a tasty cold cake that you can prepare in advance, the day before.