What is Charlotte Royale?

Ok so I am planning to get my girlfriend a cake for her birthday, which also happens to be the day after new years.

I am cooking new years day dinner which includes a whole bunch of fish. I know my gf loves lemon desserts. So I am order my fish from legals sea foods shop site who it appears has a lemon dessert.

The lemon cake/dessert is called a Charlotte Royale? Here is a picture of The Cake

Could someone explain this type of cake to me and whether or not its a good birthday cake/gift combo? It looks phenomenal but I know nothing about it.