Store tomatoes — stem end down according to some experts — in a cool, dark place, but preferably not the refrigerator. Tomatoes loose flavour if stored in very cold conditions. Five medium-sized tomatoes weigh about 500 grams and will fill about two cups when skinned and diced.
Combine the ingredients for the Gremolata and place aside.
Meanwhile, slice the mozzarella in a bowl. Sprinkle with the olive oil, basil, garlic and black pepper. Stand for at least 30 minutes to absorb the flavours.
Slice the tomatoes and layer in a flat serving dish in rows alternately with the cheese. Season with freshly ground black pepper and salt to taste. Sprinkle extra basil for garnish.
Serve lightly chilled as a light meal with crusty bread or as an accompaniment to cold meats.