Originally the sour liquid by-product of churning butter, buttermilk is now made by adding special cultures to no-fat or reduced-fat milk. You can drink it straight up (though it’s slightly tangy and not to everyone’s taste), and use it in all sorts of recipes, from soups and curries, to salad dressings, to cakes and muffins.
Buttermilk is pretty easy to find nowadays, in the dairy aisle of most supermarkets. But it might not be a regular in your refrigerator, and at times it can be easier to simply substitute it for something else. Here’s what you can do: combine 1 cup milk (whole, reduced fat, no fat or soy) and 1 tablespoon freshly squeezed lemon juice. Let it stand for 10 minutes or so, and it’s ready to go.