Trim the stems, leaves, and choke from the artichokes. Place the hearts in a small pot with enough water to generously cover. Add the lemon slices and salt to taste. Bring the water to a simmer over high heat. Reduce the heat to medium and simmer until the artichoke hearts are very tender, about 12 to 15 minutes. Cool the hearts and slice thinly or quarter.

Toss together the artichokes, tomato, red onion, scallion, cilantro, garlic, and jalapeño. Drizzle the olive oil and lime juice over the ceviche and season generously with salt and pepper. Toss until the ingredients are evenly coated. Cover the bowl and marinate the ceviche in the refrigerator for at least 2, and up to 12, hours.

Taste the ceviche just before serving and season with additional cilantro, lime juice, coarsely ground black pepper, and salt to taste. Spoon the ceviche into the endive spears and serve on a chilled platter or plates.