Head a large skillet to medium heat and spray with nonstick spray.
Butter the outsides of your bread. Spread pesto on the inside of your bread.
Then layer with Cheddar cheese, tomato, then Muenster cheese. I like to use the cheese as a barrier from the tomatoes to be sure there is no soggy bread!
Then sandwich the two pieces of bread together and place on your hot skillet. Cover with a lid so the cheese will start melting faster.
After about 2-4 minutes, your bread should be nice and browned. Flip the sandwich and brown on the other side.
Once browned and melted, it is ready to slice in half and dig in!