Preheat the oven to 350°F
Grease or line an 8×8-inch or 9×9-inch baking pan
Add 1 box of cake mix to a mixing bowl
Add 2 eggs
Add 1/2 cup melted butter or oil
Stir until a thick batter forms
Add 1 to 2 tablespoons water if the batter is too dry
Mix in chocolate chips, nuts, or other add-ins if desired
Spread the batter evenly into the prepared pan
Bake for 20 to 30 minutes
Check for doneness with a toothpick
Let the brownies cool before cutting