My mom would have named that a "Surprise Cactus!"
I think to have it bloom at Christmas there is a period of time that it gets shut in a closet or put in the garage for dormancy. You'd have to google it. There was one of these in my dad's nursing home in Michigan that was 4' high and 5' wide. A joy to behold at Christmas.
At least it bloomed sometime this year. Maybe it's a Solstice Plant.
That cactus is breathtaking!
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