Cook the bacon in a large deep frypan over medium-high heat until evenly browned; about 10 minutes. Drain the bacon slices on a paper towel-lined plate.
Preheat a barbecue for medium-high heat and lightly oil the grill. Evenly coat the salmon with the olive oil.
Cook the salmon on the preheated barbecue with the skin side down for about 5 minutes before turning and cooking on the other side until the skin can easily be lifted off the flesh; about 5 minutes more.
Flip the salmon once more and continue cooking until the salmon flakes easily with a fork; another 2 to 3 minutes.
Whisk the mayonnaise, dill and lemon zest together in a small bowl; divide between 2 of the toasted bread slices.
Top each toasted bread with a piece of cooked salmon, 2 tomato slices, 2 bacon slices, 1 lettuce leaf and a then the remaining slice of toasted bread.