Add the water, sugar, orange juice, the cinnamon stick to a saucepan and bring to the boil. Once it starts boiling, simmer uncovered for 15 minutes. Remove from heat and let cool completely.
While the syrup is being prepared, you must dry out the phyllo. Preheat your oven to 90oC. Scrunch up each filo sheet, starting from the short side, and place on a baking tray. You might need 2 baking sheets to accommodate all of your filo. Bake for 10 minutes then flip each filo sheet over and bake for an additional 8 minutes. Remove from the oven, and let sit for at least another 20 minutes. With your hands, start tearing the phyllo into small pieces, and set them aside.
Preheat oven to 180oC.
In a large mixing bowl combine the eggs and the sugar and beat for 3 - 4 minutes, until it is a pale yellow colour.
Add the orange zest, Greek yoghurt, vanilla extract, baking powder, bicarbonate of soda and salt, and mix until just combined.
Next add the oil and the orange juice to the bowl, and mix to combine well with the rest of the ingredients.
Using a rubber spatula begin to incorporate your dried out and torn filo into the cake batter, a little bit at a time. If you put all the pieces in at once, they will clump together.
After you have incorporated all of your filo into the batter, pour the mixture into a greased baking dish (I use a 30x20cm casserole dish). Bake for 50-60 minutes until your portokalopita is a nice golden colour.
Once your portokalopita is baked remove it from the oven and immediately pierce it in several places with a long clean skewer.
Pour your cooled syrup onto the hot cake, one ladle at at time. Allow each ladle to be absorbed into the cake before adding the next one. Repeat until all of the syrup has been used.
Let your cake cool for 2-3 hours before cutting, to allow the syrup to be fully absorbed.
