Heat a skillet over medium heat. Grease with a non-stick cooking spray.
Spread butter on one side of each bread slice.
Spread pesto on the unbuttered sides.
Layer cheddar cheese, tomato slices, and Muenster cheese onto one of the prepared bread slices.
Top with the other bread slice and place the assembled sandwich on the skillet. Cover to melt the cheese slices faster.
Cook for 2 to 3 minutes on each side or until the bread is golden brown.
Slice your Zupas ultimate grilled cheese sandwich in half and dig in while it's still warm. Enjoy!
Notes
Place the tomato slices between the cheese slices so your bread won't get soggy.
Cook your Ultimate grilled cheese sandwich on medium heat. The skillet should be hot enough to toast the bread but not too hot that you'll burn the bread before the cheese melts.
This copycat Zupas Ultimate grilled cheese recipe uses whole wheat bread for a nice, brown crust, but you can also use sourdough or ciabatta.