Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish with butter or non-stick spray.
Place the cubed challah or brioche bread into the greased baking dish. Distribute evenly across the dish.
In a large mixing bowl, whisk together the eggs, milk, brown sugar, vanilla extract, cinnamon, and nutmeg until well combined.
Gently fold in the diced apples and chopped pecans (if using) into the egg mixture.
Pour the egg and apple mixture over the cubed bread in the baking dish, ensuring all bread pieces are soaked. Gently press the bread down into the mixture to help it soak up the custard.
Cover the dish with aluminum foil and bake in the preheated oven for about 30 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the top is golden brown and the center is set.
Let the bake cool for a few minutes before slicing into squares. Dust with powdered sugar if desired and serve with maple syrup on the side.
Notes
Optional to add chopped pecans and powdered sugar for dusting.