Cut squash in half lengthwise; discard seeds. Place squash cut side down on a microwave-safe plate. Microwave, uncovered, on high for 14-16 minutes or until tender., Meanwhile, in a blender, combine the tomatoes, pesto, garlic powder and Italian seasoning. Cover and process until blended; set aside. In a small bowl, combine bread crumbs and Parmesan cheese; set aside., In a large skillet, cook chicken in 1 tablespoon oil until no longer pink; remove and keep warm. In the same skillet, saute mushrooms and onion in remaining oil until tender. Add garlic; cook 1 minute longer. Stir in the broth, chicken and reserved tomato mixture. Bring to a boil. Reduce heat; simmer, uncovered, for 5 minutes., When squash is cool enough to handle, use a fork to separate strands. In a large ovenproof skillet, layer half of the squash, chicken mixture and reserved crumb mixture. Repeat layers., Bake, uncovered, at 350° for 15 minutes or until heated through. Sprinkle with cheddar cheese. Broil 3-4 in. from the heat for 5-6 minutes or until cheese is melted and golden brown.