Can you use both baking powder and cream of tartar yea of no?

Yes, you can use both baking powder and cream of tartar in a recipe. Baking powder already contains an acid (usually cream of tartar) along with baking soda, so adding cream of tartar can enhance the leavening effect or provide additional acidity. However, if a recipe calls for baking powder, you typically don't need to add extra cream of tartar unless specified.