Picture here. I hope.
The flower, which is about five inches across, appeared on a pot plant I have had for a few years. It’s a variety of cactus. I thought possibly zugocactus, but it seems too large. It has flowered in our spring.
Night blooming cereus
They are usually very fragrant. I have only seen these in person in white and light pink. Yours is gorgeous.
Thanks very much for the very quick reply. I just googeled images of the creus and have doubts for a few reasons. One is that this flower had no fragrance whatsoever (although I note that you said “usually”). The other is that the pictures of the ones on google all had very much narrower petals.
Thanks though. 
Can you include a photo or description of the leaves? Whatever it is I am bent on identifying it because I want one.
Sure- I’ll do so now. The flower has wilted after just three days.
Not the kind of thing you want to admit publicly, is it?
Here is the plant overall (pleas disregard crappy background 
)
Here is a close up of the tip where I hope another bud is forming.
After using Google images to search for “red cereus” and “pink cereus” I am still fairly certain it is in the cereus family. But darned if I can figure out what variety. Cereus is a big family that includes flattened and tubular stems, and thorned and thornless. (Same family also produces dragonfruit)
I will drop into my friend’s nursery this week and show him your picture link. He collects and sells exotic blooming tropicals, and has all manner of creeping and crawling cacti in his greenhouse. We refer to his collection as “The Little Shop of Horrors”. He will be able to id it for us both.
Here are two pictures that look to be a close match, but both images are from photographers, and not from trustworthy botanical websites.
It looks like a forest cactus to me; something like a schlumbergia or rhipsalidopsis, but I can’t find an exact match.
I’d say epiphyllum or orchid cactus.
The OP’s plant is an Epiphyllum. They are very popular plants with numerous hybrids and cultivars available.
Beaucarnea: “Night-blooming cereus” is not actually a Cereus. That phrase is a common name, or nickname for Epiphyllum oxypetalum.
Plants actually belonging to the genus Cereus have similar flowers (the source of the nickname, no doubt) but they are for the most part upright columnar cacti, while most epis have flat leaves or segments, like the OP’s plant.
Thank you, KayElCee! I called my nursery friend earlier and described the plant- he also confirmed that cereus is often misapplied. Now I can ask him to order an Epiphyllum for me instead of attempting to bribe Cicero to ship me a cutting.
Beacarnia, I’d be happy to, but I’m not sure how I would get along with quarantine restrictions!
Thanks everyone- all replies were very helpful.
What am I, invisible?!
Never mind. I misread the last portion of the thread. 
I’m sorry, jayjay, I did overlook your post. I wish I had seen your response first- would have saved me nearly an hour of leafing through my moldy botany text books.
Just an update. After these things never flowering before, I now have two that are continually blooming. Must love the hot weather.