Heat oil in a largeskillet over medium-high heat. Cook onion in oil until golden.
Add broth to skillet; heat to boiling. Stir in pasta; heat to boiling. Cook uncovered 8 to 10 minutes, stirring occasionally and adding broth as necessary. Stir in broccoli and dressing, then add lemon juice and seasonings to taste.
Continue stirring until pasta is cooked, continuing to add broth as necessary.
Add feta, remove from heat, stir, and allow to rest for a couple minutes. Adjust seasonings as necessary.