Preheat the oven to 375 degrees F. Generously butter a 9-by-13-inch rectangular baking dish.
Place half the diced bread in the baking dish, and then sprinkle on half the diced apples, half the brown sugar and half the butter. Repeat with another layer of bread, apples, brown sugar and butter. End by sprinkling 1/2 cup water all over the surface, a spoonful at a time.
Bake, covered in foil, until the apples are tender, about 45 minutes. Remove the foil and bake for an additional 10 to 15 minutes to brown.