01 - Preheat the oven to 325°F. Lightly grease a 2-quart baking dish with butter.
02 - Rinse the rice under cold water until the water runs clear; drain thoroughly.
03 - In a large mixing bowl, whisk together sweetened condensed milk, whole milk, melted butter, granulated sugar, vanilla extract, cinnamon, and salt until thoroughly blended.
04 - Stir the rinsed rice and raisins, if using, into the milk mixture.
05 - Pour the combined mixture into the prepared baking dish, ensuring the rice is evenly distributed. Bake uncovered for 1 hour, stirring gently every 20 minutes, until the mixture is set and the top is lightly golden.
06 - Remove from the oven and allow to cool slightly. Serve warm or chilled, finishing with an extra dusting of cinnamon if desired.