Preheat the oven to 175 °C (350 °F) with top/bottom heat (or 160 °C/320 °F with fan). Grease the loaf pan thoroughly and dust it with flour or line it with parchment paper.
Cream the butter and sugar together for about 3 minutes until fluffy.
Add the eggs one by one, mixing well after each addition.
In a separate bowl, combine the flour, cornstarch, baking powder, and salt.
Gradually fold the dry ingredients into the butter and egg mixture. If the batter is too thick, add 1-2 tbsp of milk to achieve a smooth consistency.
Gently stir in the vanilla extract.
Pour the batter into the prepared loaf pan, smooth the top, and bake for about 40-45 minutes on the middle rack. Check with a wooden skewer to make sure it's done; the skewer should come out clean.
Let the cake cool in the pan for 10 minutes, then carefully remove it and allow it to cool completely on a wire rack.
Once fully cooled, dust with powdered sugar for a delicate finish.
