Sift the flour with the salt, vanilla, half of sugar, zest of lemon and soda.

Whisk the whites a little, add citric acid. Then whisk until soft peaks form, gradually adding sugar. To a state of stiff foam the whites do not bring it.

Add the flour in small portions, mix it to proteins in gently, trying not to reduce the amount of foam. Spoon the batter into an ungreased nothing the form with a diameter of about 20 cm, and bake in a preheated 170 degrees Celsius oven for 50 minutes. The top of the cake should be lightly browned. Once the cake has finished baking, let it cool, turning over the form with him upside down

Whisk the eggs with a whisk, to the lemon juice add the zest, butter and both kinds of sugar.

Bring the mixture with lemon juice almost to boiling and smooth. Continuously stirring the mass of the halo, a thin trickle pour in the beaten eggs. Bring cream to a simmer and thickens, without ceasing to stir. Let the cream cool down in the container with the lid closed.

Divide the cooled cake lengthwise into 3 parts, each of the two lower parts, apply the cream.

For the icing, whisk the butter with the lemon zest.

Add the powdered sugar, lemon juice and a pinch of salt, beat with a mixer until smooth. If the mass is too thick, add some more lemon juice. I advise you not to use for cooking this icing sugar powder is homemade, it is likely to squeak on the teeth.)) Brush glaze the top of the cake.