Chord name? major 1st - major 5th - dim 7th?

what is the name of a chord that has the 1st, 5th and 7th? So like Cmaj scale, C-G-B? so like a Cm7M (C-D#-G-B) no 3rd?

Dominate C drop the 3.....?

Ya. Did some work is something like C no 3rd 5/maj7 or something like that. Could be a lot of things, guess.

That would more likely be a CMaj7 (no 3rd), but because it lacks a third it could be others, like a CmMaj7, or CMaj7sus4, or CMaj9 (no 3rd).

Afro

I would say it's a major 7th power chord. C(5)maj7th

PS, the B in your example is not a diminished 7th. A diminished 7th is bb7 which would give an A.