Separate the egg whites from the yolks, mix the egg whites with the salt powder, gradually incorporating the 7 tablespoons of sugar.
Rub the yolks with the oil like mayonnaise, then mix with water. Put the baking powder over the yolks.
Add the flour over the egg whites, then the yolks and with a wooden spoon mix lightly from the bottom up.
Bake in a rectangular tray lined with baking paper for about 30 minutes on low heat until it passes the toothpick test.
Cream: Mix the butter.
In a double-bottomed bowl, put the flour and sugar, mix and add the milk gradually.
Put on low heat until it thickens like a pudding.
Leave to cool, then add the juice and lemon peel.
Homogenize with butter and leave in the fridge until the top is ready.
Assembly: Cut the top in 2 and spread the cream. Place the last sheet and prepare the "glaze"
In a bowl put whipped cream, sour cream, sugar and juice and mix on low speed then high speed.
Spread over the cake and draw some lines with a fork.
Leave in the fridge overnight.