Yellow Cactus Flower!

Went to drop the boys for a playdate in the morning and saw this beautiful flowering cactus. I didn't have my camera so when I came back in the afternoon to pick the boys, I brought my camera along. I noticed the flowers had closed up slightly from when I saw them in the morning. Could be becaue it had gotten so hot! There are even a few ants crawling in it.

A bit of research - thanks to google - indicates that this is a Yellow High Desert Flower from Beavertail Cactus.