Grease and flour the pan. Heat the oven to 350°F/175°C. Sift the flour and salt. Clarify the butter if using and cool.
Whisk the eggs and sugar to the ribbon. Whisk in the flavoring. Sift the flour over the batter in three batches and fold together as lightly as possible. Add the butter with the last batch, leaving the sediment at the bottom of the saucepan.