Preheat a large 12 inch frying pan* with a lid on for 8-10 minutes on low heat. The pan will be ready when a drop of water bubbles and sizzles in the pan.
Separate the egg whites into an electric mixing bowl and egg yolks into a regular mixing bowl.
Add the 1/4 cup sugar and 1/2 teaspoon cream of tartar into the egg whites and use the whisk attachment to beat until there are stiff peaks (5 minutes).
At the same time, add 1/4 cup milk and 1 teaspoon vanilla extract to the egg yolks and beat with a whisk until foamy. In a small bowl combine 1/2 cup flour and 1 teaspoon baking powder and add to the yolk mixture. Use a spatula to mix until mostly combined, do not overmix.
Check the frying pan, add one drop of water and if it bubbles then it's just right, replace the lid and continue making the batter. If the water drop sizzles, bounces, and evaporates immediately, lower the temperature and remove the lid for a few minutes.
When the egg whites have stiff peaks, remove the whisk attachment and transfer one large scoop of egg whites to the egg yolk mixture. Gently fold to combine and then pour the batter into the egg whites. Use a spatula to fold gently until the egg yolk batter is mixed into the egg whites. Avoid overmixing or deflating the egg whites.
When your batter is ready to cook, raise the temperature to low-medium. Check that the pan is hot enough with a drop of water. If it doesn't bubble or sizzle, cover the pan with a lid and preheat for another minute at low-medium.
Add 1 teaspoon butter and use a silicone brush to spread the melted butter in the pan. Use a large spoon to scoop approximately 2/3 cup of batter per pancake, make 3 pancakes per batch. Add an additional 1/3 cup of batter on top of each pancake and then cover the pan with a lid and cook for 5-6 minutes until the bottom is golden brown.
If at 5 minutes the pancake bottom doesn't look close to browning, add a drop of water to the pan to see if it's hot enough and adjust the temperature while cooking the other side. Flip the pancakes gently in a rolling over motion rather than lifting the spatula and dropping the pancake back in its place. Cover with a lid and cook for 5-6 more minutes.
Serve immediately with optional toppings. Wipe the pan clean with a paper towel and repeat steps 8 and 9 to cook the remaining batter.