Prepare all the ingredients.
Mix thoroughly the sugar with the soft butter using a wooden spatula. The mix must be homogeneous.
Add the egg yolks...
...and blend well.
Add the flour. Mix.
Beat the egg whites...
...with a pinch of salt until stiff.
Blend 1/4 of the eggs into the to relax it...
...and then combine the rest gently...
...with a wooden spatula.
Grease a cake mold.
Pour the dough in a buttered rectangular baking pan. Clean up the surfae to make it look even, using a wooden spatula.
Bake in warm oven (180/200°C or 356/392°F).
Bake for 40 to 35 minutes...
The dough will rise and brown. The blade of a knife should come out clean and dry if the quatre-quarts is ready.
Take out of the oven and unmold. Leave to cool.