Baking Soda and Cream of Tartar (Best Option)
1/4 teaspoon baking soda + 1/2 teaspoon cream of tartar per 3/4 teaspoon baking powderBaking powder is essentially a combination of baking soda (a base) and an acid (often cream of tartar). Using these two separately replicates the chemical reaction that produces carbon dioxide gas, which causes the cake to rise. This substitute ensures the cake has the same lightness and texture as when using baking powder.
To succeed, mix the baking soda and cream of tartar thoroughly into the dry ingredients to ensure even leavening. Avoid delays between mixing and baking to prevent loss of leavening gas.
The final cake will have a similar rise, crumb structure, and flavor profile compared to using commercial baking powder, making it the closest and most reliable substitute.