piece of cake

基本解释

Unmarried guests sometimes took home a little piece of cake to tuck under their pillow.
客人中的未婚人士有时则将这一小块蛋糕带回家，放到他们枕头底下。
Of course, you already know how to do that, so this is a piece of cake -- if you've forgotten, Listing 3 is a quick refresher.
当然，您已经知道如何去做了，所以这是轻而易举的事情 -- 如果您忘了如何去做，那么可以参看清单3作为复习。
We brought him a huge piece of cake on the most special plate we could find, and we watched him eat it to make sure he was enjoying it.
我们给他拿了一块超大的蛋糕放在一个我们能找到的最特别的盘子里，我们看着他吃下去，确保他真的觉得好吃。

"People can eat a cupcake and not feel like they're eating a whole piece of cake.
Trivial, smart animal, piece of cake.
对于这么聪明的动物，这易于反掌。
耶鲁公开课 - 心理学导论课程节选
"Piece of cake" is another expression that means something is extremely easy to do.

They would bring me a piece of cake and solemnly watch me eat it.
NEWYORKER: Wakefield