Astrophytum asterias 'Akabana'
Considered one of the most beautiful cacti. Flowers can be larger than the plant itself, and the color will range anywhere from purple to yellow or some combination of both. They have not yet flowered so the color is still unknown.
This plant is a slow grower and doesn't like a lot of water. Give it a very well draining soil mix and water sparingly during the warm season, letting it dry thoroughly in between. Winter is it's resting season and it doesn't like any water during this time.
Last photo is one example of what the flowers could look like!