Preheat oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
In a separate bowl, cream together butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla.
Gradually add the dry ingredients to the wet ingredients, alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined.
Pour batter into the prepared pan and bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean.
Let cool completely before serving.
Notes
For a richer flavor, use brown sugar instead of white sugar. You can also add chocolate chips or nuts to the batter.