Can substitute canned clams. Drain and reserve liquid. Reduce liquid to make rich clam broth.
Sauté onions in butter until softened. Add clams, continue cooking until clams release juices and juices reduce by 50%. Add Alfredo sauce, lemon juice and rich clam broth. Heat to 160ºF.
Stir in parsley.
Serve with Vermont common crackers or other neutral-flavored cracker.