Mix the balsamic, water, basil and sugar in a re-sealable container. Slice the tomatoes.

Marinate the tomatoes in the balsamic mixture at least 30 minutes, but overnight works, too (In fact, during the week that the loaf of pumpernickel is in the house, I just keep the marinade on the counter and add tomatoes whenever I use them up). Refrigeration kills the taste of tomatoes, and the acid prevents them from molding, so I just keep them on the counter as long as it’s only a day or so.

Slice the bread and cheese.

Preheat a pan to a medium low temperature. Butter one side of each slice of bread. Layer the cheese and tomatoes on the unbuttered side of the bread. Top with another slice of bread, butter side facing out.

Place the sandwich in the pan and cook until the bread is toasted and the cheese is melted. This one is awesome with my Roasted Tomato Soup.