Slice off top of each tomato; scoop out pulp, leaving shells intact. Chop pulp, and set aside. Invert shells on paper towels to drain.
Sauté pulp and onion in lard in a heavy skillet until tender. Remove from heat; stir in parsley, salt, and pepper. Spoon evenly into tomato shells; sprinkle with breadcrumbs.
Place stuffed tomatoes in a 10- x 6- x 2-inch baking dish. Bake at 350° for 30 minutes or until thoroughly heated. Serve hot.