If your recipe for cake or cookies calls for baking soda and cream of tartar, you can safely substitute baking powder for both ingredients. What's Cooking America recommends using 1 teaspoon of baking powder for every 1/4 teaspoon of baking soda plus 5/8 teaspoon of cream of tartar.

Lemon juice and vinegar act as effective cream of tartar substitutes in baking and beaten egg whites. Just make sure you use the right proportion for each situation. In baking recipes that also call for baking soda, use three times as much vinegar or lemon juice as you would cream of tarter. If you need the cream of tartar to stabilize egg whites, substitute vinegar or lemon juice in a 1-1 ratio. Adding too much liquid to egg whites can cause them to fall.

Recipes that use a lot of liquid allow you to substitute acidic dairy ingredients for cream of tartar. These include buttermilk and yogurt. To use these instead of cream of tartar, remove 1/2 cup of non-acidic liquid, like milk or water, for each 1/4 teaspoon of baking soda in your recipe. Substitute plain yogurt or buttermilk for the non-acidic liquid.

In some recipes, it's better to leave out the cream of tartar than it is to find a substitute. If your baking recipe already contains acidic ingredients, like buttermilk or lemon juice, you should be able to safely omit the cream of tartar. Many candies and frostings also do just fine without this ingredient. Beating egg whites without cream of tartar may produce a less stable result, but it should not affect the final flavor. If your recipe doesn't contain any other acidic ingredients, omitting the cream of tartar could have serious effects on the flavor and texture of your finished food.