The five-tier centrepiece, made of layers of red velvet and chocolate, is covered in white icing and features the bride and groom’s initials E and J in golden monograms around the base.
It was crafted by London-based cake designer Sophie Cabot.
Buckingham Palace said it was inspired by the rich colours of autumn and Eugenie and Jack Brooksbank will cut the cake during their afternoon reception at Windsor Castle.
The cake was mounted on a golden stand, and on show in the vast St George’s Hall.
It contains up to 400 eggs, at least 53 packs of unsalted butter, 15 kilograms of organic self raising flour, and 20 kilos of sugar.
The cake consists of three tiers of red velvet and two of chocolate sponge cake covered with butter cream and white icing.
Other ingredients include vanilla essence, vanilla bean paste and red food colouring to give the cake its distinctive hue.
Sophie came to the attention of the couple through her involvement with the Duke of York’s Pitch@Palace programme, where she supplied hand-made decorated bespoke biscuits.
The baker’s business is based in Fulham in west London.
Ms Cabot, 33, said previously she felt “very honoured they have selected me”, and said about her first meeting with Eugenie and Jack in the summer, when she brought cake samples: “The couple were very relaxed, very comfortable.
“I got the feeling the cake was something they were very excited about.”