Finely grate the zest of the lemon half over the melon pieces.
Place the arugula and basil in a large bowl or on a large platter. Season with salt and pepper, then drizzle with 1 tablespoon oil. Squeeze the lemon over. Toss gently with your hands until coated. Place the melon, mozzarella and prosciutto on top. Season with salt and pepper and drizzle with the remaining 1 tablespoon oil. Taste. If the salad is too sharp, add another drop of oil. If the salad is dull, add a sprinkle of salt. Serve right away.
