Preheat the oven to 350ºF/175ºC.
Trace and cut out a circle of parchment, grease the cake pan with butter, insert the parchment cut out and dust with flour.
Using the whisk attachment of a stand mixer, beat the eggs and sugar together until the mixture triples in volume, reaching the ribbon stage. The ribbon stage is attained when you test the batter and it temporarily holds a shape.
Sift the flour and fold it into the egg mixture in stage until incorporated.
In a separate bowl, ladle out a portion of the batter and fold it with the melted butter.
Return the buttery batter to the main mixing bowl and gently fold it with the remaining batter.
Pour the batter into the prepared cake pan and bake for 30 minutes. Check for doneness by inspecting to see if the edges have sprung away from the pan or by inserting a toothpick into the centre.
Allow it to cool on a wire rack for ten minutes before removing from the pan.