Preheat the oven to 350°F.

Spray a 9x13-inch baking dish liberally with nonstick cooking spray. Set aside.

Cut the bread into 1-inch cubes and transfer to a large mixing bowl. Set aside.

In another large mixing bowl, combine the eggs, sugar, milk, vanilla extract, cinnamon, orange zest, and salt and whisk until smooth. Add the bread cubes, and fold into mixture with a rubber spatula.

Transfer bread mixture to the prepared baking dish.

Bake the French toast on middle rack of oven until golden brown on top, and a toothpick inserted in the center of a piece comes out clean, 45-50 minutes.

Check to see that French toast is done. Remove from oven or add time as needed.

Allow French toast to cool for at least 10 minutes. Prior to serving, plate toast (cut as desired), sift powdered sugar over the top, and drizzle with maple syrup. Refrigerate leftovers for 2-3 days.