1 tsp baking soda
2 tsp cream of tartar
1 tsp cornstarch powder
Sift together 3 times through a fine sieve. Store baking powder in a clean, dry, airtight jar at room temperature, away from sunlight, up to 6 weeks.
Homemade Baking Powder may clump after it has been stored, so be sure to resift before using. Use in the same proportions as commercial baking powder.
Homemade baking powder is not double acting, and will start to react as soon as it gets wet, so work quickly and don’t let your batter sit around.