Souper-Tuna Noodle Bake
["1/2 c. chopped onion", "2 Tbsp. butter", "1 can cream of mushroom soup", "1/2 c. milk", "2 c. cooked medium noodles", "1 c. peas", "1/2 can drained, chopped tomatoes", "2 c. tuna, drained and flaked", "sliced cheese", "croutons"]
["In saucepan, cook onion in butter.", "Stir in remaining ingredients.", "Pour into 2-quart shallow baking dish.", "Bake at 400\u00b0 for 20 minutes.", "Stir.", "Top with sliced cheese and croutons.", "Bake until cheese melts."]
["onion", "butter", "cream of mushroom soup", "milk", "noodles", "peas", "tomatoes", "tuna", "cheese", "croutons"]