For a cactus bloom.
This is possibly Parodia ottonis. It was unlabeled but the flower was so pretty that I couldn't leave it behind when I was in a greenhouse in Tricities a few weeks ago. It was in bloom when I got it, and this is the second flower to open since. None of the flowers have opened fully, probably because I haven't turned on the heat yet and my house is too cool at the moment. However, unlike the Echinopsis flowers which only last one day, each of these has lasted about five days.