Preheat the oven to 180ºC (356°F) and place the rack in the middle position.
Line a large rectangular baking tray with parchment paper and set aside. Sift flour, salt, and baking powder in a bowl set aside.
Add in the whole egg, egg yolks, and sugar in a mixing machine with the whisk attachment. If you don’t have a mixing machine, you can use a bowl and hand mixer, follow the same process.
Whisk using mixer or beat using hand beater on high speed the eggs and sugar mixture for 12-15 minutes adding the lemon juice towards the last minute until mixture is light and fluffy, almost similar to a meringue texture.
Add the flour slowly in small portions into the egg mixture, folding it in from the bottom to the top, repeat until all the flour is incorporated, and well combined. Be careful not to over mix.
Using a tablespoon, add dollops of the batter onto the lined baking pan separating them apart by about 1 1/2 inch.
Bake in the preheated oven for about 9-10 minutes or until the cookie is light golden brown in color.
Remove from the oven and carefully transfer the cookies using a flat spatula to a wire cooling rack, and cool for about 10-15 minutes then transfer to a larger plate before glazing. Note, Cookies will be very soft until they are completely cooled.
Repeat until all the batter is used up.
Sugar glaze: Add the icing sugar, egg whites, and lemon juice into a medium-size bowl and whisk vigorously until the icing glaze is light, shiny, and well combined. If you notice the glaze is liquidy, add in another 1-2 tablespoons of icing sugar until it is a pasty consistency.
Glazing and decorating the cookie: To glaze the Doce Branco, spread the sugar glaze throughout the bottom first and set aside to dry for about an hour. repeat until all the bottoms of the cookies are glazed.
Once the bottoms of the cookie are dried, glaze the top of the soft cookies, and using two or three fingers, create a swirl on the surface which will give these cookies it’s distinctive seashell appearance.
You can also use the back of a teaspoon creating three swirls along the top.
Set aside and let the sugar glaze dry for another hour.
These cookies will keep well in an airtight container for up to 2 weeks.