Preheat your oven to 350°F (175°C).
In a large bowl, combine the torn bread and milk, allowing it to soak for about 10 minutes.
In another bowl, whisk together the eggs, sugar, vanilla extract, and ground cinnamon.
Add the egg mixture to the soaked bread, stirring until well combined.
Fold in the melted butter and raisins if using.
Grease a baking dish with butter or non-stick spray.
Pour the bread mixture into the prepared baking dish, spreading it evenly.
Bake in the preheated oven for 45 minutes, or until the top is golden brown.
Remove from the oven and let it cool for a few minutes.
Dust with powdered sugar before serving.