Preheat oven to 350°F (175°C).
Lightly grease an 8-inch round pan or line the bottom with parchment.

In a large bowl, beat eggs and sugar together until very light, thick, and pale
(about 4–6 minutes with a mixer — this step is key).

Beat in vanilla if using.

In a separate bowl, whisk flour, baking powder, and salt.

Gently fold dry ingredients into the egg mixture using a spatula.
Do not overmix — keep as much air as possible.

Pour batter into prepared pan and smooth the top.

Bake 25–30 minutes, until:

Top is lightly golden

Cake springs back when touched

A toothpick comes out clean

Cool 10 minutes, then remove from pan and cool completely.