Place the cornmeal, water, butter and salt in a bowl; mix with your hands for about 30 seconds until it has taken the consistency of a paste. Let it rest 5 minutes. Knead with your hands about 1 more minute until a ball of dough forms.
Make an indentation in the ball with your hand, add the cheese, and knead 1 minute more. Divide and form into 4 small balls.
Place the balls between 2 sheets of plastic and with a heavy pan or pot cover flatten to the thickness you desire, from ¼ to ½ inch.
To Cook on a Rack
Place an oiled rack on a flat pan over medium heat. When the rack is hot, put the arepas on it. Cook them about 2 minutes on each side, until they are golden brown. Serve immediately.
To Cook in a Sauté Pan
Melt ¼ teaspoon of butter in a pan set over medium heat. Place the arepas in the pan, and cook about 2 minutes on each side until they have a golden color.