Measure 1 tablespoon of baking soda, 2 tablespoons of cream of tartar and 1 tablespoon of cornstarch.
Add the ingredients to a small mixing bowl.
Use a whisk or spoon to mix the ingredients thoroughly until they are evenly combined.
Transfer the mixture to an airtight container.
Label the container with “Homemade Baking Powder” and the date it was made.
Keep the airtight container in a cool, dry place at room temperature.