01 - Preheat 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 bowl, whisk together sweetened condensed milk, whole milk, melted butter, granulated sugar, vanilla extract, ground cinnamon, and salt until evenly integrated.
04 - Fold the rinsed rice and optional raisins into the milk mixture. Transfer to the prepared baking dish, stirring gently for uniform distribution.
05 - Bake uncovered for 1 hour, gently stirring every 20 minutes to redistribute the rice, until the pudding is set and the top is lightly golden.
06 - Remove from the oven and allow to cool slightly. Serve warm or chilled, sprinkled with extra ground cinnamon if desired.