01 - Preheat the oven to 350°F. Lightly grease a 9x13 inch baking dish with butter or cooking spray.
02 - Remove phyllo sheets from packaging and let them dry out at room temperature for 1 hour until slightly crisp. Crumple the dried sheets into rough, irregular pieces by hand.
03 - In a large bowl, whisk together eggs and sugar until pale and thickened, about 3 minutes. Add Greek yogurt, oil, vanilla extract, orange zest, and baking powder. Whisk until smooth and fully combined.
04 - Gradually fold the crumpled phyllo pieces into the batter, gently mixing until all phyllo is evenly coated. The mixture will appear loose and somewhat dry.
05 - Pour the phyllo mixture into the prepared baking dish. Spread evenly and lightly press down with a spatula to create a uniform surface.
06 - Bake for 40 to 45 minutes, or until the pie is deep golden brown and a wooden skewer inserted into the center comes out clean.
07 - While the pie bakes, combine water, sugar, orange juice, cinnamon stick, and orange zest in a saucepan. Bring to a boil over medium-high heat, then reduce heat and simmer for 8 minutes until slightly thickened. Remove from heat and discard cinnamon stick and zest. Allow syrup to cool completely.
08 - Remove the baked pie from the oven. While still hot, slowly pour the cooled syrup evenly over the entire surface. The pie will hiss and absorb the syrup. Let cool to room temperature, then refrigerate for at least 2 hours or overnight before serving to allow flavors to meld.