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