This is a dish that Pop, my husband and our family's cook, has made several times. Although the recipe offers a few choices of cheese, Pop prefers using Fontina cheese since it melts so easily; he uses enough to cover the veggies with about 1/8 inch of cheese before assembling the lattice pastry top. Also, he suggests letting the tart sit after removing from the oven before cutting to let the insides set a bit.