In a pan under a low heat add the rhubarb, apples, apple concentrate, water and cinnamon. Slowly bring to the boil then reduce to simmer until all the water has absorbed. and the rhubarb and apple are tender but still retain shape.
In a food processor combine the flours. Mix the table spread with the apple concentrate and add to the food processor (with the dough blade) Process until combine and resembling breadcrumbs. Add enough ice cold water to the dough slowly until it forms a ball that is smooth and pliable. Cover with plastic and chill for 30 minutes.
Preheat oven to 180 degrees Celsius.
Roll out on a floured board making a rough circular sheet of pastry approx 40 - 50 cm in diameter. Lay the pastry onto a flat baking tray lined with baking paper. Pile the fruit mixture into the centre of the pastry and fold the ends up and around the fruit and back towards the centre.
Bake in the oven for approx 30 minutes.
Serve with yogurt or a non dairy alternative.
Note : Spelt flour and oatmeal both contain some gluten and are not suitable for people suffering from coeliac disease.