We have so many spectacular desert plants in Tucson and this particular one requires expert timing to enjoy because its bloom lasts just one day. To properly identify this beauty I looked at a few good sources and the Desert Museum's site seems to have a good match to this flower. They identify it as a "Fiery Torch" cactus. Click here for info and another photo. Notice the spent blooms at the top of the photo - they had been lush and fluffy just the day before.
Photo courtesy of Cathy Casper.