Pretty simple. But when tomatoes are in season I like to cut one up in thin slices. Then generously butter the outside of two slices of sourdough bread, put one slice butter side down on a hot pan, layer slices of smoked swiss, tomato slices, and then a bit more cheese, finishing with the last slice of bread. Brown on first side, flip, press and brown on second side.
Also sliced apple with smoked cheddar is a good one too!