1Cut a slice off of the top and bottom of each grapefruit. Stand the grapefruit upright and, following the contour of the fruit, cut away the peel and pith. Quarter the flesh and cut into slices.
2Add the jicama and mango to the bowl with the grapefruit pieces and toss to combine. Season with salt and cayenne. Drizzle with the lime juice and add the cilantro. Toss to coat. Cover and refrigerate until the salad is chilled, about 1 hour. Serve.