Begin by cutting the loaf of bread into bite-sized cubes. Place the cubes into a greased 9x13-inch baking dish, distributing them evenly.
In a large mixing bowl, whisk together the eggs, milk, granulated sugar, vanilla extract, ground cinnamon, and salt until well combined.
Pour the egg mixture over the cubed bread in the baking dish, ensuring that all pieces are well soaked.
Gently press down the bread cubes with a spatula to help them absorb the liquid. Cover the baking dish with aluminum foil and refrigerate overnight (for at least 4 hours).
The next morning, preheat your oven to 350°F (175°C). Remove the baking dish from the refrigerator and let it sit at room temperature while the oven heats.
Bake the casserole, covered with the foil, for 30 minutes. Then, remove the foil and bake for an additional 15 minutes, or until the top is golden brown and the center is set.
Once baked, allow the casserole to cool for a few minutes. Serve warm, drizzled with maple syrup and optionally dusted with powdered sugar.