Spread mayonnaise and spicy brown mustard on the other side of each slice of bread.
Layer two slices of cooked bacon, two slices of Swiss cheese, two thin slices of red onion, two thin slices of tomato, and one lettuce leaf on one slice of bread.
Top with the other slice of bread, with the buttered side facing up.
Grill sandwich on a panini press or in a skillet over medium heat until cheese is melted and sandwich is golden brown.
Cut sandwich in half and serve.
Interesting Facts
The Red Dwarf Sandwich was invented in the 1950s in the United States.
This sandwich is a great way to use up leftover bacon.
You can also add other ingredients to the sandwich, such as pickles, jalapenos, or a fried egg.