Brush a baking sheet lightly with some of the butter, lay 1 sheet of the phyllo on the butter, and brush it lightly with some of the remaining butter. Sprinkle the phyllo with 1 tablespoon of the Parmesan, lay another sheet of the phyllo on top, and press it firmly so that it adheres to the bottom layer. Butter, sprinkle, and layer the remaining phyllo in the same manner, ending with a sheet of phyllo and reserving the remaining 1 tablespoon Parmesan. Sprinkle the top sheet of phyllo with the mozzarella, scatter the onion evenly on top, and arrange the tomatoes in one layer over the onion. Sprinkle the pizza with the reserved 1 tablespoon Parmesan, the oregano, the thyme leaves, and salt and pepper to taste and bake it in the middle of a preheated 375 degree F. oven for 30 to 35 minutes, or until the edges are golden. Arrange the thyme sprigs along the pizza's perimeter and with a pizza wheel or sharp knife cut the pizza into squares.