Separate the eggs, putting the whites in a clean, dry bowl and the yolks in another bowl.

Whip the egg whites with the cream of tartar on medium speed until frothy, about 2 minutes. Gradually add 1 tbsp sugar and whip to stiff, glossy peaks, about 2 to 3 more minutes.

Whisk the egg yolks, remaining 1 tbsp sugar, milk, and vanilla until smooth. Sift in the flour and baking powder and whisk until no lumps remain.

Stir a third of the meringue into the yolk batter to lighten it, then gently fold in the rest until no white streaks show.

Place two greased ring molds in a nonstick pan over low heat. Fill each mold three-quarters full with batter. Add 1 tbsp water to the pan, cover, and cook 5 to 6 minutes. Flip the molds carefully, cover, and cook 4 to 5 minutes more.

Slide the pancakes out of the molds, stack them, and serve immediately with butter, syrup, and any toppings.