Preheat the oven to 350°F.

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

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

In a large mixing bowl, combine eggs, sugar, milk, vanilla extract, lemon zest and salt and whisk until smooth. Add to bread cubes, then add blueberries, and fold with a rubber spatula.

Transfer bread mixture to prepared baking dish.

Bake French toast on middle rack of oven until it is 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 in dish for at least 10 minutes. Prior to serving, plate toast (cut as desired), then sift powdered sugar over the top. Refrigerate leftovers for 2-3 days.