If you find yourself without baking powder and yeast but still want to make a cake, you can try using other leavening agents to help the cake rise. Here are some possible substitutes:
Baking soda: Baking soda is an alkaline leavening agent that requires an acidic ingredient to activate it. If your cake recipe contains an acidic ingredient such as buttermilk, yogurt, vinegar, lemon juice, or cocoa powder, you can use baking soda as a substitute for baking powder. The general ratio is 1/4 teaspoon of baking soda for every 1 teaspoon of baking powder.
Self-rising flour: If you have self-rising flour, it already contains baking powder, so you can use it as a substitute for both flour and baking powder in your cake recipe. If you use self-rising flour, omit any additional baking powder from the original recipe and adjust the other ingredients accordingly.
Whipped egg whites: Whipping egg whites can introduce air into the batter, acting as a leavening agent. Separate the egg whites from the yolks, beat the egg whites until stiff peaks form, and then gently fold them into the cake batter before baking. This method can provide some lift to the cake.
It's important to keep in mind that using alternative leavening agents may result in slight changes in the texture and taste of the cake compared to the original recipe. Additionally, when making substitutions, it's best to experiment with small batches first to gauge the effect on the final product.
Without yeast, it will be challenging to achieve the same rise and texture as a yeasted cake. Yeast helps create a light and airy texture in bread, which might be difficult to replicate in a cake. Therefore, using baking soda, self-rising flour, or whipped egg whites can help provide some lift, but they won't fully replace the function of yeast in a cake recipe.
If possible, it's recommended to obtain baking powder or yeast for the best results. However, in a pinch, the above substitutes can work reasonably well to still create a cake-like dessert.