Add 1 tablespoon lemon juice or white vinegar to a measuring cup.
Fill the measuring cup with milk until it reaches 1 cup. Use a small whisk or form to give it a quick stir, then let sit at room temperature for 5 minutes before using it in your recipe.
Store in an airtight container in the fridge for up to 2 weeks.
Dairy free substitute: Swap coconut milk, almond milk or soy milk for dairy milk.Yogurt substitute: For most baked good recipes like cake, you can swap 1 cup plain yogurt for buttermilk.Powdered buttermilk: You can find containers of powdered buttermilk in most stores. It will include instructions on the package to tell you the best way to incorporate it with your recipe, but typically you'll mix a certain amount in with your dry ingredients and then add the appropriate amount of water when the recipe calls for liquid buttermilk.Storing: Store in an airtight container in the coldest part of your fridge for up to 2 weeks.Freezing: Store it in a freezer-safe, airtight container in the freezer for up to three months. Portion it using an ice cube tray or place in pre-measured bags/containers for easiest use in the future.Thawing frozen buttermilk: Take the frozen buttermilk out of the freezer and place it in the fridge the night before you're going to need it. If you can't plan ahead that much, you can also place the buttermilk in a sealed container or resealable bag and place that bag inside a bowl full of warm water. It will thaw out in less than an hour, but you'll want to switch out the water occasionally as it cools so that it's replenished with warm water.