Cut each bread slice into a rectangle, about 4 1/2"x2 1/2". Arrange on a work surface.
Top bread with half of the cheese slices, trimming to fit, and 2 tomato slices. Sprinkle tomatoes with salt & pepper.
Top with remaining cheese and remaining bread. Press to compact.
Melt butter in a large skillet over medium heat. Add sandwiches. Cover and cook until bread is golden, turning once, about 3 minutes per side.
Transfer sandwiches to paper towels. Cut each sandwich in half.
Divide gazpacho among 4 bowls. Place on plates & arrange sandwiches alongside.