Preheat oven to 350°F (175°C). Grease an 8x8-inch baking dish.
In a large bowl, whisk together milk, sugar-free condensed milk, eggs, melted butter, vanilla, cinnamon, nutmeg, and salt. Stir in the cooked rice and raisins if using.
Pour the mixture into the prepared baking dish. Spread the rice evenly and sprinkle with a little extra cinnamon if desired.
Bake for 35–45 minutes, or until the edges are lightly golden and the center is set with a slight jiggle.
Let cool for 10–15 minutes before serving. Serve warm or refrigerate until chilled.
