Preheat oven to 350°F (175°C).
Line cake pan with parchment; do not grease (helps cake climb pan walls).
In a large bowl, beat eggs and sugar with an electric mixer on high speed for 8–10 minutes until pale, thick, and tripled in volume (ribbon stage).
Sift flour and salt over egg mixture in 3 batches. Gently fold with a spatula after each addition.
Add vanilla (and melted butter, if using) with the last flour batch.
Pour batter into pan; tap once to remove bubbles.
Bake 20–25 minutes until golden and springs back when touched.
Invert pan onto a wire rack immediately to prevent sinking. Cool completely before removing parchment.
