Add milk, sugar and lemon rind, stirring constantly until thickened to oatmeal consistency, about 15-20 minutes.
It will also thicken some while cooling.
Pour into one large serving plate and remove lemon rind.
Spread flat and allow to cool on wire rack.
You can be decorative with cinnamon by pinching a bit between your fingers and place while your hand is no more than an inch away from the rice (criss cross patterns are traditional), or you can just dust the entire top with the cinnamon.
Serve at room temp, but refrigerate uneaten portion.