Spread 1 side of 2 slices of bread w/ butter. Place bread, buttered-side down into a skillet. Place skillet over medium heat. Spread 1/2 of the pesto sauce on slices of bread in skillet. Place provolone cheese, tomato slices and American cheese over pesto sauce. Spread remaining pesto sauce on 1 side of remaining bread slices. Place the slices, pesto-side down onto the American cheese. Butter the top-side of bread in skillet. Fry the sandwiches for 3-5 min each side, or until golden brown and cheese is melted.