When you use plain flour instead of cake do not have to add baking powder?

Here's why:

* Plain flour has low gluten content: This means it doesn't have the ability to trap air and create a light and fluffy texture like cake flour does.

* Baking powder acts as a leavening agent: It releases carbon dioxide bubbles during baking, which causes the cake to rise and have a soft texture.

Without baking powder, a cake made with plain flour will be dense and flat.

However, there are some situations where you can use plain flour without baking powder:

* If the recipe calls for self-raising flour: Self-raising flour already contains baking powder, so you don't need to add more.

* If you're making a denser cake, like a pound cake: These cakes rely on the fat and sugar for their texture and don't need to be as light and airy.

In most cases, it's best to follow the recipe's instructions. However, if you are unsure, it's always better to add baking powder to ensure your cake rises properly.