Peanut Butter Cake
["1/4 c. butter or margarine", "1 c. sugar", "1 egg", "1 tsp. baking soda", "1 c. sour milk", "1/4 c. peanut butter", "1 1/2 c. flour", "1 tsp. vanilla", "pinch of salt"]
["To make sour milk, mix 1 cup milk with 2 tablespoons vinegar."]
["butter", "sugar", "egg", "baking soda", "sour milk", "peanut butter", "flour", "vanilla", "salt"]