Separate egg whites and yolks. Place egg whites in a very clean, dry mixing bowl and egg yolks in another bowl.

To the egg yolk bowl, add 1 tablespoon of granulated sugar, milk, and vanilla extract. Whisk until the mixture is smooth and well combined.

Sift the cake flour and baking powder into the egg yolk mixture. Whisk gently until just combined, being careful not to overmix, as this can develop gluten and make the pancakes tough.

Add the cream of tartar (or lemon juice) to the egg whites. Using an electric mixer, beat the egg whites on medium-high speed until soft peaks form.

Gradually add the remaining 1 tablespoon of granulated sugar to the egg whites while continuing to beat. Continue beating until stiff, glossy peaks form, creating a stable meringue.

Gently fold about one-third of the meringue into the egg yolk batter until lightly combined. This lightens the batter.

Add the remaining meringue and fold gently using a spatula until no streaks of white remain, being careful not to deflate the airy batter.

Lightly grease a non-stick pan or griddle and heat it over very low heat. It's crucial to keep the heat low.

Drop large spoonfuls of batter onto the pan, forming thick, round pancakes. For extra height, you can stack a second spoonful directly on top of each pancake.

Add about a tablespoon of water to the pan next to the pancakes, not directly on them, and immediately cover with a lid. Cook for 3-4 minutes until the pancakes are puffed up and lightly golden on the bottom.

Carefully flip the pancakes using a wide spatula. Add another tablespoon of water to the pan, cover again, and cook for another 3-4 minutes until cooked through and golden brown.

Serve the Japanese Souffle Pancakes immediately with your desired toppings, such as butter, maple syrup, fresh berries, or whipped cream.