Mix water, cornmeal, mozzarella cheese, butter, and salt together in a large bowl. Knead until well combined and a soft dough forms.
Form dough into balls the size of a medium orange.
Place each ball between two sheets of plastic wrap and flatten with a rolling pin to the desired thickness.
Leaving plastic wrap in place, press the top edge of a cereal bowl or drinking glass into the surface of the dough to cut circles.
Remove the plastic wrap and remove any excess dough scraps.
Spray a griddle with cooking spray and set over medium-high heat.
Working in batches, cook arepas on the hot griddle until golden brown, about 5 minutes per side.
Serve immediately.
