01 - Preheat oven to 325°F. Lightly grease a 2-quart baking dish with butter.
02 - Rinse rice under cold water until water runs clear. Drain thoroughly.
03 - In a large mixing bowl, whisk together sweetened condensed milk, whole milk, melted butter, sugar, vanilla extract, cinnamon, and salt until blended.
04 - Stir rice and, if desired, raisins or sultanas into the prepared liquid mixture.
05 - Pour mixture into the prepared baking dish, ensuring rice is evenly distributed.
06 - Bake uncovered for 1 hour, stirring gently every 20 minutes until pudding is set and surface is lightly golden.
07 - Remove from oven and allow to cool slightly. Serve warm or refrigerate until chilled. Sprinkle with additional cinnamon before serving if desired.