1. Cook bacon in small nonstick skillet over medium-high heat until very crisp. Remove to paper towels; when cool, crumble.
2. Remove virtually all of the bacon grease, but do not wipe out skillet.
3. Combine mayonnaise and salsa. Spread on one side of bread. Top with half of the cheese, then avocado slices. Sprinkle crumbled bacon on top. Arrange remaining cheese over bacon.
4. Cover with second slice of bread. Spread top with 1 teaspoon of the butter
5. Heat skillet over medium heat. Add sandwich, butter-side down, and cook about 2 minutes or until lightly browned. Spread remaining butter on top side of sandwich. Turn over. Cook another 2 minutes or until cheese is melted.