Part 2/8:
Next, incorporate 55 g of all-purpose flour—about one-third of a cup—into the mixture. Be careful not to over-mix, as excessive manipulation can develop gluten, resulting in a less fluffy cake. Once the mixture is smooth, set it aside.
In a separate bowl, beat the egg whites along with 10 g of lemon juice. The acidity from the lemon will help structure the meringue. Whip the egg whites until they reach soft peaks, at which point you can start adding 50 g of granulated sugar. Continue whipping until the sugar is fully dissolved and stiff peaks form.