01 - Preheat oven to 325°F. Lightly grease a 2-quart baking dish with butter.
02 - Rinse short-grain 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, ground cinnamon, and salt until fully blended.
04 - Stir in the rinsed rice and, if desired, raisins or sultanas until evenly distributed.
05 - Pour the rice mixture into the greased baking dish, gently stirring to ensure even distribution.
06 - Bake uncovered for 1 hour, stirring gently every 20 minutes, until the 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.