SUBSTITUTE FOR BUTTERMILK
My grandma taught me this trick years ago, because who has buttermilk just lying around? Personally, I don't drink the stuff. So, here's what I do to substitute:
1 cup milk + 1 Tbsp. lemon juice or vinegar.
Pour the lemon juice or vinegar in a measuring cup, then add enough milk to make a cup. Stir, let set for 5 minutes to sour the milk, then use it in your recipe.