Preheat a skillet or griddle over medium high heat.
Spread the bread evenly with about ½ teaspoon each of butter. Put the bread butter-side-down, and sprinkle with half of the cheese. Evenly spread the guacamole over the cheese. Top with tomato slices and remaining cheese. Top with the other slice of bread, butter-side-up.
Transfer bread {with the buttered sides on the outside} to the skillet and cook about 3-5 minutes per side, until cheese is melted and bread is toasted. Enjoy!