Preheat the oven to 350°F (175°C). Grease and flour a 9x13 inch pan.

In a large bowl, cream together the softened butter and sugar until smooth and fluffy.

Beat in the eggs one at a time, mixing well after each addition.

Add the vanilla extract and stir until fully incorporated.

In another bowl, combine the flour, baking powder, and salt. Gradually add this dry mixture to the creamed mixture while alternating with the milk, starting with the flour mixture.

Pour the batter into the prepared pan, smoothing the top with a spatula.

Bake for 30 to 40 minutes or until a toothpick inserted in the center comes out clean.

Allow the cake to cool in the pan for a few minutes before transferring it to a wire rack to cool completely.