Heat up cast iron skillet to medium high low. Add butter or a tablespoon of bacon grease to the pan.
Butter one side of each slice of bread and flip butter side down. Add sliced avocado, roast beef and gouda. Sprinkle with salt and fresh ground pepper to taste.
Toast each side of the sandwich with a lid on the pan to trap enough heat to melt the cheese. Cut in half and serve.
