First you need to preheat oven to 350F.
Spray THREE 9 x 1 1/2-inch round pans or your 9x13 with cooking spray or grease with butter.
In a large bowl combine the flour, sugar, baking powder & the salt until well combined.
Add the milk, vegetable oil, butter & the vanilla to the flour mixture and Mix VERY well
(I recommend using an electric mixer), but you can do it by hand, just be sure its completely mixed.
Finally, add in the eggs & continue mixing until well combined
Pour batter into your greased pans/pan and bake at 350F for 17 to 22 minutes OR until a tooth pick comes out clean when inserted.