Top and tail rhubarb and cut tender stems into small pieces. Place in a non-reactive saucepan and add water, sugar and lemon rind, cover and let simmer for a few minutes. To make the crumble, mix together in a bowl, the flour, sugar, rolled oats, almonds, macadamia and pistachio nuts. Rub in some butter keeping the mixture light. Once the rhubarb has softened, remove the lid and allow any excess juices to reduce. At this stage remove the lemon, add in the apples and mix in well. Place the rhubarb/apple mixture into a greased oven dish, topped with the crumble mix and pat down. Cook for about 35-40 minutes at 190c until golden brown. Serve with natural yoghurt. Per serving: 2461 Calories (kcal); 205g Total Fat; (71% calories from fat); 45g Protein; 141g Carbohydrate; 219mg Cholesterol; 845mg Sodium Food Exchanges: 5 1/2 Grain(Starch); 3 1/2 Lean Meat; 0 Vegetable; 3 Fruit; 38 1/2 Fat; 1 Other Carbohydrates Converted by MM_Buster v2.0n.