Preheat your oven to 350°F (175°C).
Grease and flour a 9x13 inch baking pan.
In a large mixing bowl, cream the softened butter and sugar together until light and fluffy.
Add the eggs one at a time, beating well after each addition.
In a separate bowl, sift together the flour, baking powder, and salt.
Gradually add the dry ingredients to the butter mixture, alternating with the milk.
Stir in the vanilla extract until well combined.
Pour the batter into the prepared baking pan.
Bake for 45-50 minutes or until a toothpick inserted in the center comes out clean.
Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack.