Make the sandwich starting with a layer of cheese, then add the turkey, the tomato in the middle, and then another layer of cheese to create a moisture barrier to prevent the bread from getting soggy.
Press and grill:
Brush the outside of the sandwich with a little butter or olive oil. Grill it in a panini press or skillet with a heavy pan on top to press it down. Cook until golden on one side, flip, and repeat. Cheese should be gooey and the outside should be crisp.
Serve:
Let it cool slightly before slicing it in half on a plate or cutting board. Enjoy!