Preheat the oven to 350°F.
Microwave the butter until melted, then mix in the sugar.
Pour this into a 13x9-inch pan and use a pastry brush to spread it all over.
Beat the milk with the vanilla and eggs.
Arrange half the bread in the pan in one layer.
Spread half the egg mixture over the bread.
Sprinkle over half the cinnamon.
Add the rest of the bread slices on top then the rest of the egg mixture.
Cover the dish with foil and refrigerate overnight.
Bake covered for 30 minutes then uncovered for another 15.
Sprinkle with cinnamon and powdered sugar.
Serve hot, with warmed maple syrup if liked.