Ready to whip up this delightful dish? Follow these simple steps:

1. Start by spreading butter on one side of each bread slice. This will help achieve that perfect golden crust.
2. In a small bowl, mash the avocado with a fork and season with salt and pepper. If you like a bit of heat, sprinkle in some red pepper flakes.
3. Lay two bread slices, buttered side down, on a cutting board. Spread the mashed avocado evenly over them.
4. Layer the cheese slices over the avocado, followed by the tomato slices. Top with the remaining bread slices, buttered side up.
5. Heat a non-stick skillet over medium heat. Place the sandwiches in the skillet and cook for about 3-4 minutes on each side, or until the bread is golden brown and the cheese has melted.
6. Once done, remove from the skillet and let them cool for a minute before slicing. This gives the cheese a chance to set slightly, making for a cleaner cut.

Pro tip: Press gently with a spatula while grilling to ensure everything melds together beautifully, just like my grandmother taught me when making her famous quesadillas.