Preheat oven to 350°F. Prepare an 9x13 glass baking dish with a light coating of cooking or baking spray.
In the bowl of your mixer, cream together butter and sugar. Add eggs,1 at a time, and beat until light and fluffy.
Add flour, baking powder and salt and beat until incorporated.
Turn your mixer on low and slowly add in milk. Continue to beat just until mixture is well blended.
Pour cake batter into prepared baking pan and bake for 45 minutes to an hour, or until knife inserted into the center comes out clear.
Remove from the oven and cool.