Do not use tub margarine or light spreads in baking because they do not have the properties of fat. If calories are not your concern, you can substitute an equal amount of trans fat-free vegetable shortening or 3/4 cups of oil for every one cup of butter. Canola oil is best because of its bland flavor. Fruit purees, like applesauce, pureed prunes and baby-food fruits, are often used in place of butter. For every 1/2 cup of fruit puree, add one to four tablespoons of oil and cut back a bit on the sugar.