Cook the bacon in a large skillet over medium heat until crisp, 6 to 8 minutes. Transfer to a paper towel–lined plate.
Wipe out the skillet and heat the oil over medium heat. Season the salmon with ¼ teaspoon each salt and pepper.
Cook until opaque throughout, 2 to 3 minutes per side.
Spread the bread with the mayonnaise and top with lettuce, tomato, salmon, and bacon.