In the bowl of a stand mixer cream the butter and sugar until light and fluffy. Reduce the speed to low and add the eggs one at a time and mix thoroughly to combine. Add the vanilla extract. Add the flour, baking powder, and salt and mix just until well incorporated. Pour batter into prepared pan and spread in an even layer. Don't be alarmed by how little batter there is in the pan, this is normal. Bake for 20-25 mintures or until a toothpick comes out clean.
1 cup (220g) sugar, ½ cup (1 stick) (113g) butter, room temperature, 5 large eggs, room temperature, 1 tablespoon vanilla, 1½ cups (215g) all purpose flour, 1 teaspoon baking powder, ½ teaspoon salt