Prepare the Syrup:

In a saucepan, combine the sugar, water, orange juice, orange zest, and cinnamon stick. Bring the mixture to a boil, stirring occasionally.

Reduce the heat and simmer for 5-7 minutes until the sugar has dissolved. Remove from heat and let the syrup cool completely.

Prepare the Cake:

Preheat the oven to 350°F (175°C). Grease a 9x13-inch baking dish.

Tear the phyllo dough into small pieces and spread them on a baking tray to dry slightly.

In a large bowl, whisk together the eggs, sugar, yogurt, orange juice, olive oil, orange zest, vanilla extract, and baking powder until smooth.

Add the torn phyllo dough to the mixture, ensuring that the pieces are evenly coated with the custard.

Bake:

Pour the mixture into the prepared baking dish and spread it evenly.

Bake in the preheated oven for 40-45 minutes, or until the top is golden and a toothpick comes out clean.

Add the Syrup:

Once the cake is out of the oven, immediately pour the cooled syrup over the hot cake. Make sure the syrup soaks into all parts of the cake.

Allow the cake to cool to room temperature before transferring it to the refrigerator to chill for at least 2 hours, or overnight for best results.

Serve:

Cut into squares and serve chilled, optionally garnished with orange slices or a sprinkle of cinnamon.