The cakes-and-pies category is thirteen lines long, and none of them are sold by the slice. If you want one, you take the whole thing.
That is a decision, not a shortage
A cut cake has a clock on it. Keeping them whole means the one you carry out was not sitting open on a tray for a day, and it means the counter is not throwing away four slices every night to sell eight.
The second one is half price
There is an offer running on the account right now: buy one cake or pie, get 50% off a second. It applies at the item level and needs no code — the register finds it. If you are feeding a party, that is the one to know about.
Ordering ahead
Everything on the list can be ordered online, and the counter quotes about ten minutes for a normal ticket. A whole cake is not a normal ticket. Give it real notice, especially at the end of the week.
The full list, with prices, is on the menu page. It is the same list the register reads.