Potato-Onion Piquante
["6 medium potatoes", "2 medium onions, thinly sliced", "2 Tbsp. margarine", "1 (4 oz.) pkg. buttermilk Ranch Style dressing", "1 c. mayonnaise", "1 c. buttermilk"]
["Make several crosswise slices in each potato, not cutting quite all the way through bottom peel (each slice to be approximately 1/2 inch thickness).", "Gently open cuts and place one onion slice in each.", "Place in a shallow dish.", "Cover and bake at 450\u00b0 for 1 hour or until potatoes are done.", "Dot with margarine."]
["potatoes", "onions", "margarine", "buttermilk", "mayonnaise", "buttermilk"]