sounds like it is a flower spike. the dry weather has induced the plant to flower early. yes pull it out from the base rather than cut it.

Just curious, Sbg. Rhubarb is very difficult to grow here, but my limited experience is that you harvest the leaves by pulling them off, but doing that to the flower stalk will break the root. There's a good chance that I have been doing it wrong, though! :/

I have never had a problem twisting it out but perhaps I have been lucky. :o)

(smack forehead) Twist! That's it! Just twist! (to misquote Gimli).
Ah, well. I always did have to learn gardening the hard way. :S

Thanks all: In meantime my wife found an old gardening book which recommended removing the flowering stem as it said it would weaken the plant. So I twisted it off. Agree with comment that it's due to very dry weather. Good to have your confirmation

If you did not harvest any stalks last year you did the right thing. Don't worry abut the flowers, you did that right too.