Preheat oven to 150°C. Grease the base and sides of a shallow baking tray with oil.
In a medium saucepan over high heat, bring to the boil water, sugar and lemon juice. Boil for 10 minutes, until the syrup thickens. Remove from the heat and set aside to cool.
Using a sharp knife, cut filo pastry sheets to fit the dimensions of the baking dish.
Place two sheets of filo pastry in the bottom of the greased pan and brush it with melted butter.
Continue until you have used 4 filo sheets, brushing every two sheets with butter.
Spread a quarter of the walnuts over the 4th buttered sheet, and then sprinkle a quarter of the AdVital Powder.
Repeat until all the remaining filo sheet are used. Finish with two sheets of filo pastry, and brush the last layer with melted butter.
Using a sharp knife cut horizontal and vertical parallel lines, right through all the layers to the bottom, to form square shapes.
Bake the baklava in the oven for 45 -60 minutes or until the top is golden brown.
When the baklava is ready, remove it from the oven, and slowly pour the cooled syrup over the piping hot pastry. Allow to stand for 2-3 hours to soak up the syrup, and to cool.
Once the baklava is cool, sprinkle baklava pieces with ground pistachios. Always at room temperature.