Cut squash lengthwise in half; discard seeds. Place squash on a microwave-safe plate, cut side down. Microwave, uncovered, on high for 15-18 minutes or until tender., Meanwhile, in a lightly oiled nonstick skillet, cook and stir onion over medium heat until tender. Stir in salsa, beans and cilantro; heat through. Gently stir in avocado; cook 1 minute longer., When squash is cool enough to handle, use a fork to separate strands. Serve squash topped with salsa mixture.