Peel onions, and cut each into 8 wedges. Gently peel outer skin from garlic and discard. Cut off and discard top one-fourth of garlic head. Place onion and garlic, cut sides up, in center of a piece of heavy-duty aluminum foil; coat with cooking spray. Fold foil over onion and garlic, sealing tightly. Bake at 350° for 1 hour or until onion and garlic are soft. Remove from oven, and let cool.
Remove and discard skin from garlic. Scoop out garlic pulp with a small spoon. Position knife blade in food processor bowl; add garlic pulp, onion, and cheese. Pulse 5 times or until combined. Add broth and next 3 ingredients to garlic mixture. Process until mixture is finely chopped. Set aside.
Cook pasta according to package directions, omitting salt and fat; drain. Add garlic mixture; toss lightly. Serve immediately.