Season watermelon discs (10 cm diameter, 3 cm thick) and brown both sides in hot oil
Cook over low heat for half an hour; set aside
Prepare vinaigrette with sherry vinegar, olive oil, and salt; combine with cherry tomatoes, red onion, arugula, mozzarella, and black olives; let rest 5 minutes
Place watermelon disc on plate, top with prepared mixture, garnish with anchovies and basil leaves
