Fluffy Japanese Pancakes

Whisk together egg yolks, milk, and vanilla extract in a bowl.
Add sifted cake flour, salt, and baking powder.
Using a handheld mixer, combine the flour and egg mixture for 2 minutes; Set aside.
In a clean bowl, combine egg whites and cream of tartar until foamy.
Slowly add the powdered sugar to the meringue.
Beat until the mixture forms into medium peaks.
Whisk together a quarter of the meringue to the butter mixture.
Using a spatula, slowly fold the remaining meringue over the batter.
In a nonstick pan over low heat, add a tablespoon of oil.
Brush the ring molds with oil and place it on the pan for a couple of minutes. Slowly add the batter to fill three-quarters of each mold.
Place a lid on the pan and cook for 3 minutes.
Add a tablespoon of water into the pan to create steam and put back the lid.
Cook for another minute, turn the pancake over and pour another tablespoon of water and cook for another minute with the lid. Repeat the process with the remaining batter.
Serve with your favorite choice of sweet sauce.