1/ Place the Rhubarb ,the orange juice, and zest into a saucepan and cover with a tight fitting lid and cooke gently for approx. 15 mins then leave to cool
2/In a clean bowl ( oil and fat free), whisk the egg whites with the salt until they start to hold then gently little by little add the castor sugar whisking throughout the process (as though you were making Meringue).
3/ When the rhubarb is cool gently fold into the whisked egg white using a metal spoon.
4/ Brush the sides of either an 850 ml ( 1.5 pt) the soufflé dishe or alternatively 4 individual soufflé dishes with the melted butter then dust with the sugar.
5/Pour the mixture into the dish and bake in the pre-heated oven for approx. 12 mins.
When ready serve immediately.