Beat the eggs with the sugar, butter, and flour until you obtain a creamy consistency. Heat the milk in a pan with the cinnamon and lemon rind then add the egg mixture. Stir constantly to prevent sticking and lumps until it reaches the boil.
Grease a round terracotta dish and pour the mixture in. Dust with cinnamon and bake in the oven for around 40 minutes.
Serve sliced with Rainha Cláudia sugar plums in syrup.