Preheat the oven to 180°C.
Melt the butter in the microwave.
Whip the eggs and sugar together until creamy.
Add the melted butter and vanilla extract and mix well.
Sift in the cake flour and gently fold, being careful not to deflate the mixture.
Pour the batter into a pan lined with parchment paper.
Bake in the oven at 180°C for 25–30 minutes.
Let the cake cool on a wire rack before serving.