This is a locally grown tomato which is similar to “coeur de boeuf”, a varying variety that comes in various forms and shapes: http://fr.wikipedia.org/wiki/Liste_des_vari%C3%A9t%C3%A9s_de_tomates
In this case, the large variety is larger than the fist of an adult. It can become mealy, or over ripe or bruised if not handled carefully after being picked. These tomatoes do not travel well despite their sizes. They are delicate and they ripen quickly, so they require handling with care and packing is critical for any-kind of travel. The skin on large tomatoes can sometimes be a touch tough but eat them as fresh as possible and slice them evenly as possible, by a horizontal slice. The surface is wide and so you can make a meal out of them. The tomato above has no bruising, no uneven ripening and was delicious with a pinch of salt, and if you prefer add some extra virgin olive oil.