Queen of Night

This beautiful flower is definitely from a cactus, but not Hylocereus [in which dragon fruit belong to]. This spotting is that of Epiphyllum oxypetalum http://en.wikipedia.org/wiki/Epiphyllum_oxypetalum "Epiphyllum oxypetalum (Dutchman's Pipe, kardable, Night Queen or निशागंधी Nishagandhi or Gul-e-Bakawali) is a species of cactus and one of the most cultivated species in the genus. It is a variety of nightblooming Cereus and often confused with species of Selenicereus."

I agree with Dan

I think its a type of Nightblooming Cactus - Hylocereus http://en.wikipedia.org/wiki/Hylocereus