Each letter is a key on the on-screen piano below. Lowercase letters are white keys, capital letters are black keys. Open the piano and press them in order — no sheet music needed.
E D C · E D C · C C C C · D D D D · E D CHot Cross Buns uses exactly three notes in a descending line and then drills each of them four times. It looks trivial and it is exactly the point: with only three notes you can hear every flaw in your timing. It is the first tune most piano methods teach, for good reason.
Play E D C twice (u y t in our keyboard letters), then C four times, D four times, and finish with E D C again.
Three notes across two fingers' reach leaves no room to hide uneven timing, so it is a very quick check on whether the pulse is steady.