Preheat your oven to 350°F (175°C) and prepare a cupcake tray with paper liners.

In a large mixing bowl, crack and whisk together the eggs and sugar, beating for approximately 8-10 minutes until pale and thick.

Gently fold in the vanilla extract into the egg mixture.

In a separate bowl, sift together the flour and salt, then gradually fold the dry ingredients into the egg mixture, being careful not to deflate the batter.

Add the melted butter, gently folding until just mixed.

Spoon the batter into the prepared cupcake liners, filling them about 2/3 of the way full.

Place the tray in the oven and bake for 15-18 minutes, or until a toothpick inserted into the center comes out clean.

Once baked, remove the sponge cakes from the oven and allow them to cool in the tray for a few minutes before transferring to a wire rack to cool completely.