a piece of cake
idiom

- something that is easy to do

(MacMillan Dictionary)

---
In the mid-19th century, cakes were commonly given as prizes in contests. A "cakewalk" was a competition to see who could show the most elegant or fanciest steps around a cake that was placed in the middle of a circle drawn with chalk.

Initially, the dancers were slaves who were mocking the arrogant mannerisms of the high society in the US southern states. At the time, the term "cakewalk" was also used to refer to an activity that was stylish and fun, but simple to do.

At some point this became the phrase "a piece of cake", which was then used by the British armed forces in the Second World War.
            
If learning that expression was a piece of cake, try to remember other popular idioms that include the word "cake":

- take the cake = something that is unexpectedly good or bad (I thought I was unprepared, but Tom’s lack of interest really takes the cake)

- icing on the cake = a pleasurable event added to something already good (I had hoped for recognition, but getting the promotion was the icing on the cake) Another word for icing is "frosting"

- have your cake and eat it, too = to expect things that are opposite (You can work part-time or you can earn more. You can’t have your cake and eat it too)

---
SYNONYMS

easy, simple, little effort, a walk in the park,

---
SMUGGLE OWAD into today's conversation

"We expected problems transporting the equipment, but with our new logistics company it was A PIECE OF CAKE."