Add the carrot, cork and white onion to a large pot of well-salted water and bring to a boil over high heat. Reduce the heat to medium, add the octopus and cook, uncovered, until tender, about 40 minutes. Test for doneness by cutting into a tentacle at the thickest part, near the head; if it cuts easily and spreads open, the octopus is done. Remove the octopus from the pot and chill immediately.
Once chilled, slice the tentacles from the body, discarding the head or reserving it for another use. Thinly slice the tentacles into 1/4-inch-thick rounds and transfer them to a large bowl. Add the kiwis, dragon fruit, tomato, red onion and melon to the bowl.
Add the cilantro, chili sauce, olive oil, sriracha, lime juice and grapefruit juice to the bowl. Mix well, using your hands or a large spoon, and season with salt. Refrigerate the ceviche for 30 minutes to allow flavors to develop.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.