Preheat the oven to 350°F (175°C). Grease a baking dish.
In a large bowl, soak the bread cubes in milk for 10 minutes.
In another bowl, whisk together sugar, eggs, vanilla, cinnamon, and salt.
Pour the egg mixture over the soaked bread and mix well. Add raisins if using.
Transfer the mixture to the prepared baking dish and drizzle melted butter on top.
Bake for 40-45 minutes until golden brown and set in the center.
Let cool slightly before serving. Enjoy warm or chilled!