In a large mixing bowl, combine melted butter, eggs and vanilla.
In a separate bowl, combine flour, Nesquik, baking powder, sugars, and salt
Slowly incorporate the egg mixture into the flour mixture and stir until well combined (batter will be thick)
Preheat oven to 350 F
Grease a 9x13 pan with non-stick cooking spray
Pour batter into pan and cook for 25-30 minutes or until toothpick inserted in the center comes out clean