Cook pasta according to the package directions, omitting salt and fat. Drain; keep warm.
Cook bacon in a large nonstick skillet over medium heat until crisp. Remove bacon from pan; crumble. Add onion to drippings in pan; sauté 1 minute. Add asparagus and broth to pan; bring to a boil. Reduce heat, and simmer 5 minutes or until asparagus is crisp-tender. Add pasta, spinach, 1/4 cup cheese, and pepper to pan; toss well. Sprinkle with remaining 1/4 cup cheese and bacon.