You will need 3” x 2.5” wide ring molds, I linked to ones I use above.
In a large bowl whisk the flour, sugar, baking powder, baking soda and salt.
In a medium bowl whisk the buttermilk, butter, vanilla, and egg yolk until combined.
In a medium bowl beat the egg whites and cream of tartar on medium-high speed until stiff peaks form. About 2-3 minutes.
Using a rubber spatula stir the buttermilk mixture into the flour mixture until partially combined. Stir the egg whites into the batter until combined. Be careful not to overmix as this will result in tough and chewy pancakes.
Heat a large nonstick skillet over medium-low heat. Spray the pan (or cooking surface) with nonstick spray. Spray the inside of a 3”in ring mold generously with nonstick cooking spray.
Spoon in the batter. Place the ring mold on the warm pan and fill each mold with ½ cup of batter. DO NOT OVERFILL. The batter should fill the mold halfway to the top. Cover the skillet with a lid (if it has a lid) and cook until the batter rises to the top and the bottom of the pancake is golden, about 5-8 minutes. There should be some bubbles that have formed on the tops of the pancakes. The center will just barely jiggle. (Note: if you flip too soon, the uncooked batter will ooze out into the pan).
Using a spatula, carefully release the bottom of the pancakes. Grasp the sides of the ring molds with kitchen tongs then carefully flip. (If cooking 1 at a time you can rest the pancake on the spatula and bring the skillet up to the pancake and turn the pancake onto the skillet). NOTE: I have a short video of how to do this. Cover and cook the other side for another 3-5 minutes.
Release the pancakes. Transfer to a plate and remove the mold. Best way to get the pancakes out is by running a butter knife around the inside of each mold to release each pancake, then carefully remove the mold. Wipe down each mold and coat with cooking spray before repeating the process with the remaning batter.
Serve warm with a sprinkling of powdered sugar and fruit, or butter and maple syrup. Pancakes can deflate with time.