A hint of lemon is perfect in a creamy baked custard. This one has no caramel to get in the way of the lemon flavor. Lemon juice would be too overpowering here. Instead, the subtle lemon flavor comes from steeping lemon zest in the milk for the custard mixture. The heat of the milk extracts the essential oil from the lemon zest skin, and the milk absorbs the delicate flavor. The hints of cinnamon and vanilla are there to support the lemon, not obscure it. Raspberry sauce makes a perfect complement. I wouldn't dream of serving the custard without it.