01 - Preheat oven to 325°F. Lightly grease a 2-quart baking dish with unsalted butter.
02 - Rinse short-grain rice under cold water until water runs clear, then drain thoroughly.
03 - In a large mixing bowl, whisk together sweetened condensed milk, whole milk, melted butter, granulated sugar, vanilla extract, ground cinnamon, and salt until well combined.
04 - Fold rinsed rice into the milk mixture. Stir in raisins or sultanas if using.
05 - Pour mixture into the prepared baking dish. Gently stir to ensure even distribution of rice and fruit.
06 - Bake uncovered in the preheated oven for 1 hour, stirring gently every 20 minutes. Bake until pudding is set and the surface is lightly golden.
07 - Remove from oven and allow to cool slightly. Serve warm or chilled, garnished with extra ground cinnamon if desired.