When I worked at that restaurant in the Napa Valley, I had a couple favorite dishes - and up top was the heirloom tomato sandwich. I recreated the sandwich here at home, and after some tweaking, I think it's really good.
Havarti or fontina
1. First - put some garlic through a press, mix it with some mayo. Let that sit.
2. Lightly toast a piece of bread, spread with "garlic aioli". Next, slice the tomatoes. Here you can go two routes. If you're going to do it traditionally, you'll reduce the balsamic vinegar to make a syrup. If you're going to do it the easy way (how I did it this week), drench the tomatoes in vinegar and let them drip off a bit before setting on the bread. Add cheese, then make a basil chiffonade and sprinkle over the top. In the picture above, I used olive oil, but I don't recommend it - looks nice but the flavor just isn't right. Finally, pop the whole thing in the toaster oven until the cheese is soft but not melted and EAT UP!
3. Die of deliciousness.
I realize that middle step is really long, but this is my first "recipe", so bear with me. :)