In a medium bowl, whisk together flour, baking powder, and salt, then set aside.

In a separate large bowl, whisk milk, egg yolks, 2 tablespoons sugar, melted butter, and vanilla extract until smooth.

In a clean, dry large bowl, beat egg whites with an electric mixer until foamy; add cream of tartar (if using), then gradually add 1/4 cup sugar until stiff, glossy peaks form.

Whisk dry ingredients into wet ingredients until just combined, then gently fold in about a third of the meringue to lighten the batter, followed by the remaining meringue in two additions.

Heat a non-stick pan over low-medium heat and lightly grease it; place pancake rings (if using) and spoon generous amounts of batter into them, filling two-thirds full.

Add a tablespoon or two of water around the pancakes in the pan, immediately cover, and cook for 4-5 minutes on low heat.

Remove the lid, gently loosen rings if used, then flip the pancakes and cook for another 3-4 minutes, covered, until golden brown and cooked through.

Transfer to plates and serve immediately.