Many recipes call for buttermilk because acid is needed to react with baking soda in your recipe to create a nice light product with plenty of moisture. Since buttermilk is not a basic kitchen staple, here is a tip for creating buttermilk for your recipes: place one tablespoon of lemon juice into your one cup measure then fill to the brim with milk for one cup of buttermilk. Skim or fat free milk used the same way will create: fat-free buttermilk. If you’re out of lemons, orange juice or vinegar would substitute equally well for the lemon juice. To create other measurements of buttermilk, please use the following ratio: 1 part lemon juice to every 15 parts milk.