01 - Combine 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 frequently, until rice is tender and mixture has thickened considerably. Remove and discard the lemon peel and cinnamon stick.
03 - Stir in granulated sugar, butter, and vanilla extract. Continue cooking for 2–3 minutes, stirring until sugar has completely dissolved.
04 - Whisk egg yolks in a separate bowl. Gradually add 2–3 spoonfuls of the hot rice mixture while whisking continuously to temper the yolks and prevent curdling.
05 - Return tempered yolks to the saucepan. Cook over low heat, stirring constantly, for 2–3 minutes until mixture thickens slightly. Do not allow to boil or eggs may scramble.
06 - Pour the custard into individual ramekins or a large shallow serving dish, spreading evenly.
07 - Mix 2 tablespoons granulated sugar with ground cinnamon. Sprinkle evenly over the surface of the custard.
08 - Let custard cool to room temperature before serving. Can be served warm or refrigerated and served chilled.