Combine the vinegar and sherry in a saucepan and bring to a boil. Add the diced vegetables and salt and pepper, bring back to a boil, and reduce to a simmer. Cook, uncovered, until thick, about 20 minutes. Adjust seasonings and let relish cool. To serve, coat a large platter or individual plates with relish. Top with the Iberian ham slices. Leftover relish will keep in the refrigerator for a few weeks.