Preheat oven to 350 degrees F (175 degrees C). Grease and flour one 9 inch round cake pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs, one at a time, then stir in the vanilla. Combine the flour, baking powder, and salt; stir into the creamed mixture alternately with the milk.
Pour batter into prepared pan. Bake for 30 to 35 minutes in the preheated oven, or until a toothpick inserted into the center of the cake comes out clean.
Cool in pan for 10 minutes, then turn out onto a wire rack and cool completely.
Interesting Facts
This cake is traditionally served with a glass of warm milk to help you fall asleep.
It is believed that the baking powder and sugar in this cake can help create serotonin in the body, which promotes sleep.
The cake can be stored in an airtight container for up to 3 days.