⭐ Baking Soda + Cream of Tartar (Best Fat-Free Option)
1/4 teaspoon baking soda + 1/2 teaspoon cream of tartar per 1 teaspoon baking powderBaking powder is essentially a combination of baking soda (a base) and an acid (commonly cream of tartar). Using baking soda with cream of tartar replicates this acid-base reaction, producing carbon dioxide gas that helps lighten the sauce slightly and maintain its delicate texture.
For best results, mix the baking soda and cream of tartar thoroughly before adding to the sauce to ensure even leavening. Avoid adding excess amounts, as too much baking soda can impart a metallic or soapy taste.
Compared to commercial baking powder, this substitute provides a fresher, more controlled reaction, allowing the Béarnaise Sauce to retain its classic creamy and airy qualities without unwanted flavor changes.