In a Dutch oven, saute celery and onion in butter until tender. Remove from the heat. Stir in the bread cubes, parsley, sage, thyme, salt and pepper. Add broth; toss to coat.
Cut a thin slice off the top of each tomato. Scoop out pulp, leaving a 1/2-in. shell. Invert tomatoes onto paper towels to drain. Spoon about 1/3 cup stuffing into each tomato. Place in a greased 11x7-in. baking dish. Place remaining stuffing around tomatoes. Bake, uncovered, at 350° for 25-30 minutes or until tomatoes are tender.