Make the artichokes: Bring a large pot of water to a boil; season with salt. Juice lemon into water; add rind. Meanwhile, trim artichoke stems to 1/2 inch. Remove tough outer leaves. Trim pointy tips of artichoke leaves using kitchen shears. Cut artichokes in half lengthwise, and remove chokes by scraping with a small spoon. Transfer artichokes to lemon-water as you work, to prevent discoloration. Cook until hearts are easily pierced with a sharp knife, about 12 minutes. Drain, and let cool.
Meanwhile, heat grill to medium-high. Make the aioli: Whisk together yolk, lemon juice, mustard, and oregano (or pulse in a food processor). Slowly pour in oil in a slow, steady stream, whisking constantly until emulsified; season with salt and pepper.
Drizzle artichokes with oil. Season with salt and pepper; toss. Grill, turning, until lightly charred and caramelized, about 5 minutes.
Arrange ham on a platter; top with artichokes. Serve with aioli.