Begin by cutting your 100% whole wheat bread into thick slices, about 1 inch each. If your bread is a day or two old, that’s even better!
In a large mixing bowl, combine the eggs, evaporated milk, 2% milk, granulated sugar, ½ teaspoon of ground cinnamon, maple syrup, vanilla extract, lemon or orange zest, and kosher salt. Whisk until well combined.
Arrange half of the bread slices in a single layer in the baking dish. Pour half of the custard mixture over the bread, ensuring each slice is well soaked.
Layer the remaining bread slices on top and pour over the remaining custard mixture. Gently press down on the bread to ensure it absorbs the custard.
Cover the baking dish with plastic wrap and refrigerate overnight.
Preheat your oven to 350°F (175°C). Remove the plastic wrap and sprinkle the remaining ½ teaspoon of ground cinnamon over the top of the soaked bread. Bake for 40-45 minutes, or until the top is golden brown and the custard is set.
Once baked, let the Overnight French Toast cool for a few minutes before slicing. Serve warm with pure maple syrup, a pat of butter, fresh berries, a dollop of Greek yogurt, or a sprinkle of powdered sugar.