What can you use instead of baking powder in a cake?

There are a few substitutes you can use instead of baking powder in a cake:

- Baking soda and an acidic ingredient: Baking soda is a base, so it needs to be combined with an acidic ingredient in order to create a reaction that will produce carbon dioxide gas and cause the cake to rise. Some common acidic ingredients that can be used include buttermilk, yogurt, lemon juice, or cream of tartar.

- Self-rising flour: Self-rising flour is a type of flour that already contains baking powder and salt, so you don't need to add any additional leavening agents.

- Egg whites: Beaten egg whites can be used as a leavening agent in cakes, but they will not produce as much rise as baking powder.

- Yeast: Yeast is a living organism that produces carbon dioxide gas as it grows, so it can be used as a leavening agent in cakes. However, yeast can take several hours to activate, so it's not as convenient as baking powder.

It's important to note that substituting one leavening agent for another may affect the texture and flavor of your cake, so you may need to experiment to find the best substitution for your recipe.