Preheat your oven to 350°F (175°C). Grease and line an 8-inch round cake pan with parchment paper.
In a mixing bowl, beat the sugar and eggs together until the mixture triples in volume—don’t rush this, it’s key to that perfect sponge texture.
Sift the flour, baking powder, and salt together. Gently fold the dry ingredients into the egg mixture in batches to avoid losing air.
In a small saucepan, heat the milk and butter until the butter melts. Remove from heat and stir in vanilla extract.
Slowly pour the warm milk mixture into the batter, folding gently until combined.
Pour the batter into your prepared pan and bake for 30–35 minutes, or until a toothpick comes out clean.
Let the cake cool in the pan for 10 minutes before transferring it to a wire rack. Cool completely before serving or frosting.