Spray a 9x13 baking dish with cooking spray then layer the bread slices on the bottom of the pan. (It's ok if pieces overlap and you can also halve them to fill in gaps.)
In a medium bowl, whisk together eggs, milk, apple butter, vanilla, cinnamon and nutmeg. Pour mixture on top of the bread making sure that each slice is fully immersed in the liquid.
Sprinkle evenly with raspberries, walnuts and brown sugar.
Cover and refrigerate overnight.
The next morning, pre-head oven to 350 degrees and bake, uncovered, for 45 minutes. Serve with maple syrup and butter if you wish.