In a medium pot, cover the potatoes with salted water and bring to a boil. Cook until just fork-tender, about 5 to 7 minutes. Drain and refresh under cold running water.
When cool, combine the potatoes, pineapple, onion, and bell pepper in a large bowl.
In the bowl of a blender, combine the egg and lime juice. With the machine running on high speed, add the vegetable oil in a slow, steady stream. When all the oil has been added and the mixture is thickened, add the soy sauce, sesame oil, ginger, salt, and cayenne, and process 30 seconds to combine. Pour the mayonnaise over the potato mixture and toss well to combine. Add the cilantro and toss again. Cover tightly and refrigerate for 1 hour to allow the flavors to marry.