The C major seventh sharp eleventh chord is a 5-note chord consisting of the notes C, E, G, B and F#.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Cmaj#4.
Chords that are a superset of Cmaj#4. The chords include more notes but always C, E, G, B and F#.
Chords that are a subset of Cmaj#4. These contain less notes but all of them are included in Cmaj#4.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the Cmaj#4 chord. Feel free to save or share the image as needed.