Preheat oven 160C (140C fan forced).

Put half the sugar into a clean, dry, medium saucepan and melt gently, occasionally swirling the pan so that the sugar melts evenly. When the sugar has melted allow it to cook until a dark golden caramel. Remove the pan from the heat and stir in the lemon juice and 3 tablespoons of water. Return the pan to the heat and continue to cook until the caramel is a smooth thick syrup.

Heat milk and lemon rind in a small saucepan until just simmering, remove from the heat. Meanwhile, whisk together the egg yolks, eggs, remaining sugar and vanilla bean paste until combined. Gradually stir in the milk mixture until combined, then strain mixture through a fine sieve into a jug.

Pour the hot caramel mixture into the base of four x 400ml heatproof glasses. Set aside to cool then pour the egg mixture on top. Line a large saucepan or casserole pan with 3 layers of paper towel. Place the glasses into the pan and add enough hot tap water to come up to the same level as the custard in the glass. Bake for about 45 minutes or until just set.

Remove the custards from pan and allow to cool. Refrigerate for several hours or overnight.