01 - Combine the rice, whole milk, heavy cream, lemon peel, cinnamon stick, and salt in a medium saucepan. Bring to a gentle simmer over medium heat, stirring occasionally to prevent sticking.
02 - Reduce heat to low and cook for 25–30 minutes, stirring often, until the rice is tender and the mixture has thickened considerably. Remove and discard the lemon peel and cinnamon stick.
03 - Stir in the granulated sugar, butter, and vanilla extract. Continue cooking for 2–3 minutes, stirring until the sugar has completely dissolved.
04 - Whisk the egg yolks in a separate bowl. Gradually ladle a few spoonfuls of the hot rice mixture into the yolks while whisking continuously to temper them and prevent curdling.
05 - Return the tempered yolks to the saucepan and cook gently over low heat, stirring constantly, for 2–3 minutes until the custard coats the back of a spoon. Do not let it boil.
06 - Pour the custard evenly into individual ramekins or a large shallow serving dish.
07 - Mix the remaining 2 tablespoons of granulated sugar with the ground cinnamon. Sprinkle evenly over the surface of the custard.
08 - Allow the rice custard to cool to room temperature, then refrigerate if serving chilled. Serve warm or cold as desired.