7largeegg whites at room temperature or 1 ¼ cups(260 grams)
½teaspooncream of tartar
½teaspoonvanilla extract
½teaspoonlemon juice
Instructions
Adjust the oven rack so that it's the second to the lowest, then preheat to 375 degrees F.
Mold 2 large sheets of foil around an overturned 8-inch square metal so that you have a 3 inch overhang on all 4 sides. Turn the pan over and press the foil into the pan, shaping so that the foil goes up slightly to make a bit of a wall. It doesn't have to be a strong wall, it's just a bit of reinforcement for the batter.
Whisk together the flour, salt and sugar.
In a stand mixer fitted with the whisk attachment, beat the egg whites and cream of tartar on one of the lower speeds for about a minute. Increase speed and beat just until stiff peaks just start to form -- don't overbeat. The peaks should just barely hold. Beat in the lemon juice and vanilla.
Remove the mixer from the stand and use a large, heavy duty scraper to fold in the flour in ⅓ cup increments. The batter will deflate somewhat as you fold. Try to keep it airy, but also make sure you get the flour mixture blended in evenly.
Spread the batter evenly in the prepared pan and bake for 35 minutes.
Invert and let cool upside down with the foil and pan covering. When cool, remove the pan and peel away the foil.